Wastepaper deinking method using amine or acid salt of amine in the flotation stage

ABSTRACT

A deinking method comprising the steps of liberating ink from waste paper as a raw material and removing the liberated ink from a flotation system, wherein a nonionic surfactant, e.g., a reaction product obtained by adding an alkylene oxide to a mixture of an oil &amp; fat and an alcohol, an alkylene oxide adduct of a fatty acid, or an alkylene oxide adduct of a higher alcohol, is used for the liberation of ink, and the flotation step is effected in the presence of a cationic compound, an amine, an acid salt of an amine or an amphoteric compound at a pH of from 4 to 9, provides a high quality deinked pulp having a high whiteness and a little residual ink spots.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a deinking method for deinking waste papers such as news papers, leaflets and magazines to reclaim them. More particularly, it relates to a deinking method excellent in workability by which an excellent deinked pulp having a higher whiteness and a less residual ink spots is obtained at a high yield.

2. Description of the Related Art

Waste papers are reclaimed by liberating ink from the waste papers by a deinking treatment to prepare reclaimed pulp and manufacturing reclaimed paper from the reclaimed pulp. The conventional deinking method generally comprises a step of liberating ink from waste papers and another step of rejecting the liberated ink.

More specially, the deinking method comprises, as main steps,

(1) a step of pulping (disintegrating) waste papers,

(2) a step of aging, i.e., leaving the disintegrated paper as it is,

(3) a step of flotation, and

(4) a step of washing.

That is, in deinking treatment, ink bound to the fibers of waste papers is physically and chemically (or biochemically) liberated therefrom to thereby separate the ink from the fibers. Thus, reclaimed pulp is obtained.

In effecting deinking treatment, a deinking agent comprising a surfactant such as a polyoxyethyl alkyl ether and a fatty acid is generally used in any of the above-described steps, for the purposes of liberating ink from waste papers or generating foams to which the liberated ink will adhere.

In recent years, the properties of waste papers which are used as raw materials have been varied because of an increase in a demand for a beautiful and stable printing and a progress in printing techniques. In addition, degrees of binding of ink to paper are varied, including loose ones and tight ones. Under these circumstances, it is demanded to improve the quality and the recovery (i.e., the productivity) of deinked pulp. In order to attain such a purpose, various proposals are offered from various fields including deinking processes, deinking agents and apparatuses used for deinking.

In conventional deinking methods, the pulping step and the flotation step are usually carried out at an alkaline pH of exceeding 9, and in an extremely few cases, at a pH of 9 or less. Deinking methods wherein the pulping step and the flotation step are carried out at a pH of 9 or less are disclosed in Japanese Patent Publication-A Nos. 54-23705 and 59-53532, and U.S. Pat. No. 4,043,908 (published on Aug. 23, 1977; Assignees: Kemanord Aktiebolag and Sala International AB). Specially, Japanese Patent Publication-A No. 54-23705 discloses a method wherein an aluminum salt or white water is added to a waste paper dispersion, the pH of the dispersion is adjusted to a pH ranging from 4 to 7, a polyelectrolyte is added to the dispersion, and then the flotation is effected. Japanese Patent Publication-A No. 59-53532 discloses that a specific alkylamine polyether, which behave as an amine at a basic pH and as an quaternary ammonium at an acidic pH, contributes to the appearances of foam performances required during the pulping step, deinking step of washing-system and flotation step, respectively. U.S. Pat. No. 4,043,908 discloses a method wherein an ethylene oxide adduct of an amine is used for liberating ink from pulp, and the disintegration of waste papers and the liberation of ink therefrom is carried out at a high pH to thereby introduce the ink into micelles, and then the pH of the system is reduced to break the micelles, thereby separating (precipitating) the ink from the pulp, and the ink is removed out of the system by flotation.

According to the method disclosed in Japanese Patent Publication-A No. 54-23705, however, the lathering power is markedly high, and therefore a decrease in the recovery of pulp and an increase in the amount of foams to be rejected (or discharged) during flotation step occur. Such an excess generation of foams is not preferred for flotation and brings about reductions in productivity and quality. The alkylamine polyether disclosed in Japanese Patent Publication-A No. 59-53532 is inferior to conventional polyoxyethylene alkyl ether type deinking agents in the ink-liberating performance and therefore can not provide a pulp having a high whiteness. Further, the ink liberated from pulp with the use of such an alkylamine polyether is in the form of very fine drops and does not have an optimum size suitable for the adsorption to the foam during flotation. Accordingly, the ink can not sufficiently be removed during flotation. The method disclosed in U.S. Pat. No. 4,043,908 does not attain sufficient deinking. The reason is not necessarily clarified. but it is considered to be due to when an ethylene oxide adduct of an amine is used as the deinking agent in the disintegrating step wherein ink is liberated from pulp, the ink is not sufficiently liberated therefrom. and that when the pH of the system is reduced for flotation, the ink which is dispersed in the system or dissolved in the micelles once again adheres to the pulp.

WO 94/28237 teaches a flotation deinking process which comprises the steps of:

1. forming a pulping slurry of printed media and water

2. adding to the slurry (i) a specific non-ionic surfactant of the formula RO[(AO)_(n)-R^(o)]m; and (ii) a fatty acid or salt thereof of the formula R⁵COOM wherein R⁵ is a linear or branched alkyl (alkenyl) and M is hydrogen or a counterion; and

3. subjecting the slurry to flotation deinking in a flotation cell characterized by:

(A) using a specific printed media

(B) adding a water-soluble cationic polymer to the slurry prior to the flotation deinking.

During the pulping step the pH is maintained at about 7.5 to 11. After the slurry exists the pulper it is diluted to about 1 weight % solids. A specific pH reduction step is not taught.

WO 93/21376 describes a process of deinking waste paper comprising:

1. forming a pulp from the waste paper in a aqueous medium that has a pH of between 6 and 9 and that is substantially free of dissolved phosphate and includes an ink-dispersing amount of dispersing agent; and

2. separating the ink from the pulp (e.g., by flotation, page 6 line 9).

In this process preferably a surfactant, generally a non-ionic surfactant such as an ethoxylated phenol or fatty alcohol may be used.

DISCLOSURE OF THE INVENTION SUMMARY OF THE INVENTION

Under the above-mentioned circumstances, the present inventors have made extensive investigations from the viewpoint of the deinking method. As a result of the investigations, the present inventors have found that a deinked pulp having a higher whiteness and a less residual ink spots can be obtained by liberating ink sufficiently from waste papers with the use of a nonionic surfactant as a deinking agent, and effecting the flotation step at a pH of from 4 to 9 in the presence of a cationic compound, an amine, an acid salt of an amine or an amphoteric compound. The present invention has been completed on the basis of this finding.

Thus, the present invention provides a deinking method comprising the steps of liberating ink from. waste paper as a raw material and removing the liberated ink from a flotation system, which comprises adding at least one nonionic surfactant for liberating ink from said waste paper; adjusting the pH of a system to pH 4 to 9 before or during said step for removing the liberated ink from a flotation system; and adding at least one member selected from the group consisting of cationic compounds, amines, acid salts of amines and amphoteric compounds before or during said step for removing the liberated ink from a flotation system.

In other word, the present invention relates to a deinking method comprising at least steps of liberating ink from waste paper as a raw material and removing the liberated ink from a flotation system, wherein at least one nonionic surfactant is used for the liberation of ink; and at least part of the flotation step is effected in the presence of at least one member selected from the group consisting of cationic compounds, amines, acid salts of amines and amphoteric compounds at a pH in a range of from 4 to 9.

The nonionic surfactant is preferably selected from the group consisting of nonionic surfactants (A) to (D):

nonionic surfactant (A): a reaction product obtained by adding an alkylene oxide to a mixture of an oil & fat and an alcohol,

nonionic surfactant (B): a compound represented by the formula: RCOO(AO)_(m)R′ (wherein R represents an alkyl or alkenyl group having 7 to 23 carbon atoms; R′ represents a hydrogen atom, an alkyl group having 1 to 22 carbon atoms, an alkenyl group having 2 to 22 carbon atoms, or an acyl group having 2 to 22 carbon atoms; AO represents an oxyalkylene group having 2 to 4 carbon atoms; and m is an integer of 1 or more),

nonionic surfactant (C): a compound represented by the formula: RO(AO)_(n)H (wherein R represents an alkyl or alkenyl group having 8 to 24 carbon atoms; AO represents an oxyalkylene group having 2 to 4 carbon atoms; and n is an integer of 1 or more), and

nonionic surfactant (D): a reaction product obtained by adding an alkylene oxide to a polyvalent carboxylic acid or an acid anhydride thereof; or a reaction product obtained by adding an alkylene oxide to a mixture of a polyvalent carboxylic acid or an acid anhydride thereof, and alcohol.

The addition form of alkylene oxides in an alkylene oxide adduct among the nonionic surfactants described above may be a block one or a random one, or alternatively a mixture thereof.

At least one member selected from the group consisting of cationic compounds, amines, acid salts of amines and amphoteric compounds is desirably added to the flotation system after adjusting the pH of the system to a value in a range of from pH4 to pH9. In this case, at least one member selected from the group consisting of cationic compounds, amines, acid salts of amines and amphoteric compounds is preferably used in an amount such that the pH of the flotation system is scarcely altered by the addition of such at least one member.

The cationic compounds are desirably selected from the group consisting of compounds represented by the following formulas (a₁) to (e₁) and cationic polymers represented by the following formulas (f₁) to (j₁) each of which has a cationic nitrogen content of 0.01 to 35% by weight and a weight-average molecular weight of 2,000 to 3,000,000; the amines and acid salts of amines are desirably selected from the group consisting of compounds represented by the following formulas (a₂) to (h₂) and polymers represented by the following formulas (i2) to (l₂) each of which has an amino-nitrogen content of 0.01 to 35% by weight and a weight-average molecular weight of 2,000 to 3,000,000; and the amphoteric compounds are desirably selected from the group consisting of compounds represented by the following formulas (a₃) to (j₃), phospholipids (k₃), proteins (l₃) and amphoteric polymers represented by the following formulas (m₃) and (n₃) each of which has a cationic nitrogen content of 0.01 to 35% by weight and a weight-average molecular weight of 2,000 to 3,000,000:

in formulas (a₁) to (e₁), R₁ and R₂ may be the same or different from each other and each represents an alkyl, alkenyl or β-hydroxyalkyl group having 10 to 24 carbon atoms; R₃, R₄ and R₅ may be the same or different from one another and each represents an alkyl or hydroxyalkyl group having 1 to 8 carbon atoms, a benzyl group, or a group represented by the formula: —(AO)_(n)—Z (wherein AO represents an oxyalkylene group having 2 to 4 carbon atoms, z represents a hydrogen atom or an acyl group, and n is an integer of from 1 to 50); R₆ represents an alkyl, alkenyl or β-hydroxyalkyl group having 8 to 36 carbon atoms; X⁻ represents a counter ion; and Y represents an alkyl, alkenyl or β-hydroxyalkyl group having 8 to 36 carbon atoms, a group represented by the formula: R₆COOCH₂— (wherein R₆ is as defined above), a group represented by the formula: R₆CONHCH₂— (wherein R₆ is as defined above) or a group represented by the formula: R₆OCH₂— (wherein R₆ is as defined above);

in formulas (f₁) to (j₁), R₁, R₂, R₃, R₆, R₇, R₈ and R₉ may be the same or different from one another and each represents an alkyl group having 1 to 24 carbon atoms or an alkenyl group having 2 to 24 carbon atoms; R₄ and R₅ may be the same or different from each other and each represents a hydrogen atom or a methyl group; X⁻ and W⁻ may be the same or different from each other and each represents a counter ion; Y and Z may be the same or different from each other and each represents O or NH; AO represents an oxyalkylene group having 2 to 4 carbon atoms; p and q may be the same or different from each other and each represents an integer of 1 to 10; r represents an integer of 0 to 10; and 1, m and n are each such a positive number that the weight-average molecular weight of the polymer would be a value in the range of from 2,000 to 3,000,000;

in formulas (a₂) to (h₂), R₁ represents an alkyl, alkenyl or β-hydroxyalkyl group having 8 to 36 carbon atoms; R₂ and R₃ may be the same or different from each other and each represents a hydrogen atom, an alkyl group having 1 to 24 carbon atoms or an alkenyl group having 2 to 24 carbon atoms; HA represents an inorganic or organic acid; AO represents an oxyalkylene group having 2 to 4 carbon atoms; 1 and m are each zero or a positive integer with the proviso that 1 plus m is an integer of 1 to 300; and W₁, W₂, W₃ and W₄ may be the same or different from one another and each represents a hydrogen atom or an alkyl group having 1 to 24 carbon atoms;

in formulas (i₂) to (l₁₂), R₁ represents an alkyl group having 1 to 24 carbon atoms or an alkenyl group having 2 to 24 carbon atoms; R₂, R₃ and R₆ may be the same or different from one another and each represents a hydrogen atom, an alkyl group having 1 to 24 carbon atoms or an alkenyl group having 2 to 24 carbon atoms; R₄ and R₅ may be the same or different from each other and each represents a hydrogen atom or a methyl group; HA represents an inorganic or organic acid; Y represents O or NH; p represents an integer of 1 to 10; and l, m and n are each such a positive number that the weight-average molecular weight of the polymer would be a value in the range of from 2,000 to 3,000,000;

in formulas (a₃) to (j₃), R₁, R₂ and R₃ may be the same or different from one another and each represents an alkyl group having 1 to 24 carbon atoms or an alkenyl group having 2 to 24 carbon atoms; R₄ represents an alkyl, alkenyl or β-hydroxyalkyl group having 8 to 36 carbon atoms; M represents a hydrogen atom, an alkali metal atom, ½ mole of an alkaline earth metal atom or an ammonium group; Y₁ represents a group represented by the formula: R₅NHCH₂CH₂— (wherein R₅ represents an alkyl group having 1 to 36 carbon atoms or an alkenyl or β-hydroxyalkyl group having 2 to 36 carbon atoms); Y₂ represents a hydrogen atom or a group represented by the formula: R₅NHCH₂CH₂— (wherein R₅ is as defined above); Z₁ represents a group represented by the formula: —CH₂COOM (wherein M is as defined above); and Z₂ represents a hydrogen atom or a group represented by the formula: —CH₂COOM (wherein M is as defined above); and

in formulas (m₃) and (n₃), R₁, R₂ and R₃ may be the same or different from one another and each represents a hydrogen atom, an alkyl group having 1 to 24 carbon atoms or an alkenyl group having 2 to 24 carbon atoms; R₄ and R₅ may be the same or different from each other and each represents a hydrogen atom or a methyl group; M represents a hydrogen atom, an alkali metal atom, ½ mole of an alkaline earth metal atom or an ammonium group; X⁻ represents a counter ion; Y represents 0 or NH; p is an integer of 1 to 10; and m and n are each such a positive number that the weight-average molecular weight of the polymer would be a value in the range of from 2,000 to 3,000,000.

The present invention includes a deinking method comprising at least a step of liberating ink from waste paper as a raw material and a step of removing the liberated ink therefrom by flotation, characterized in that one or two or more deinking agent(s) selected from among the above nonionic surfactants (A) to (D) is(are) used; the pH in the system during flotation is controlled to 4 to 9; and a cationic compound(s) is(are) allowed to be present in the system during flotation. In this case, the cationic compound(s) is(are) preferably one or more compounds selected from the group consisting of those represented by the above formulas (a₁) to (e₁).

The present invention also includes a deinking method comprising at least a step of liberating ink from waste paper as a raw material and a step of removing the liberated ink therefrom by flotation, characterized in that one or two or more deinking agent(s) selected from among the above nonionic surfactants (A) to (D) is(are) used; the pH in the system during flotation is controlled to 4 to 9; and an amine(s) or an acid salt(s) of an amine(s) is(are) allowed to be present in the system during flotation. In this case, the amine(s) or the acid salt(s) of the amine(s) is(are) preferably one or more compounds selected from the group consisting of those represented by the following formulas (a₂) to (h₂):

wherein R₁ represents an alkyl, alkenyl or β-hydroxyalkyl group having 8 to 36 carbon atoms; R₂ and R₃ may be the same or different from each other and each represents a hydrogen atom or an alkyl group having 1 to 24 carbon atoms; HA represents an inorganic or organic acid; AO represents an oxyalkylene group having 2 to 4 carbon atoms; 1 and m are each such an integer that 1 plus m would be a numerical value of above zero and 300 or below; and W₁, W₂, W₃ and W₄ may be the same or different from one another and each represents a hydrogen atom or an alkyl group having 1 to 24 carbon atoms.

The present invention includes, further, a deinking method comprising at least a step of liberating ink from waste paper as a raw material and a step of removing the liberated ink therefrom by flotation, characterized in that one or two or more deinking agent(s) selected from among the above nonionic surfactants (A) to (D) is(are) used; the pH in the system during flotation is controlled to 4 to 9; and an amphoteric compounds) is(are) allowed to be present in the system during flotation. In this case, the amphoteric compound(s is(are) preferably one or more compounds selected from the group consisting of those represented by the following formulas (a₃) to (j₃), phospholipids (k₃) and proteins (l₃):

wherein R₁, R₂ and R₃ may be the same or different from one another and each represents an alkyl group having 1 to 24 carbon atoms; R₄ represents an alkyl, alkenyl or β-hydroxyalkyl group having 8 to 36 carbon atoms; M represents a hydrogen atom, an alkali metal atom, ½ mole of an alkaline earth metal atom or an ammonium group; Y₁ represents a group represented by the formula: R₅NHCH₂CH₂— (wherein R₅ represents an alkyl, alkenyl or β-hydroxyalkyl group having 8 to 36 carbon atoms); Y₂ represents a hydrogen atom or a group represented by the formula: R₅NHCH₂CH₂— (wherein R₅ is as defined above); Z_(l) represents a group represented by the formula: —CH₂COOM (wherein M is as defined above); and Z₂ represents a hydrogen atom or a group represented by the formula: —CH₂COOM (wherein M is as defined above).

As described above, increase of lathering during flotation is observed in deinking treatment according to the method disclosed in Japanese Patent Publication-A 54-23705. As a result of investigations made by the present inventors, it is confirmed that the above phenomenon is caused by using a nonionic or anionic polyelectrolyte such as polyacrylamide (PAM) under such a condition that the aluminum ion concentration of the system is high in flotation. In contrast, the deinking method of the present invention, wherein a nonionic surfactant is employed as a deinking agent, and the flotation is effected at a pH of from 4 to 9 in the presence of a cationic compound, an amine, an acid salt of an amine or an amphoteric compound, provides such a marked effect that deinked pulp having a high quality can be obtained at a high recovery. It is considered that the above effect can be attained by the present invention because ink is sufficiently liberated from fibers of waste paper by the use of a nonionic surfactant, and the liberated ink is efficiently collected for the removal thereof because of the presence of a cationic compound, an amine, an acid salt of an amine or an amphoteric compound at a pH falling within a range of from 4 to 9 in flotation.

Further scope and applicability of the present invention will become apparent from the detailed description and examples given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description and these examples.

DETAILED DESCRIPTION OF THE INVENTION

The deinking method of the present invention comprises at least steps of liberating ink from waste paper and removing the liberated ink from a flotation system.

Next, the nonionic surfactants to be used as deinking agents in the present invention will now be illustrated.

Nonionic surfactant (A) A reaction product obtained by adding an alkylene oxide to a mixture of an oil & fat and an alcohol.

Nonionic surfactant (A) is an alkylene oxide adduct of a mixture of an oil & fat and a mono- or polyhydric alcohol. The alkylene oxide is added to the mixture described above in an amount, on the average, of 5 to 300 moles, preferably 20 to 150 moles, per mole of the mixture. Examples of the alkylene oxides include ethylene oxide, propylene oxide and butylene oxide, and they may be used singly or in the form of a mixture of two or more of them.

The mixing ratio of the oil & fat to the alcohol is preferably 1/0.1 to 1/6, particularly preferably 1/0.3 to 1/3 by mole. When this ratio falls with in the range described above, a reclaimed pulp having an excellent appearance can be obtained since the liberation of ink is efficiently attained.

Examples of the oils & fats as a raw material of nonionic surfactant (A) include vegetable oils such as coconut oil, palm oil, olive oil, soybean oil, rape seed oil and linseed oil, animal oils such as lard, beef tallow and bone oil, and fish oils; hardened oils thereof and semi-hardened oils thereof; and recovered oils obtained in refining processes of these oils & fats.

Examples of the monohydric alcohols as a raw material of nonionic surfactant (A) include those having an alkyl or alkenyl moiety of 8 to 24 carbon atoms and those having an alkylphenyl moiety wherein the alkyl moiety has 6 to 14 carbon atoms. Specific examples thereof include 1-octanol, 1-nonanol, 1-decanol, 1-undecanol, 1-dodecanol, 1-tridecanol, 1-tetradecanol, 1-pentadecanol, 1-hexadecanol, 1-heptadecanol, 1-octadecanol, 1-nonadecanol, 1-eicosanol, 1-heneicosanol, 1-docosanol, 1-tricosanol, 1-tetracosanol, 2-octanol, 2-nonanol, 2-decanol, 2-undecanol, 2-dodecanol, 2-tridecanol, 2-tetradecanol, 2-pentadecanol, 2-hexadecanol, 2-heptadecanol, 2-octadecanol, 2-nonadecanol, 2-eicosanol, 2-octen-1-ol, 2-dodecen-1-ol, 2-undecen-1-ol, 2-tetradecen-1-ol, 2-pentadecen-1-ol, 2-hexadecen-1-ol, 2-octadecen-1-ol, 8-nonen-1-ol, 10-undecen-1-ol, 11-dodecen-1-ol, 12-tridecen-1-ol, 15-hexadecen-1-ol, oleyl alcohol, elaidyl alcohol, linoleyl alcohol, linolenyl alcohol, eleostearyl alcohol, ricinoyl alcohol, cyclononanol, cyclodecanol, cycloundecanol, cyclododecanol, cyclotridecanol, cyclotetradecanol, cyclopentadecanol, cyclohexadecanol, cycloheptadecanol, cyclooctadecanol, cyclononadecanol, cycloeicosanol, octylphenol and nonylphenol.

Examples of the polyhydric alcohols as a raw material of nonionic surfactant (A) include ethylene glycol, propylene glycol, trimethylene glycol, butylene glycol, 1,6-hexanglycol, 2-ethylbutane-1,2,3-triol, glycerol, trimethylolpropane, trimethylolethane, 1,2,4-butanetriol, 1,2,6-hexanetriol, 1,1,1-trimethylolhexane, tetramethylolcyclohexanols, diglycerol, mannitane, pentaerythritol, erythritol, arabitol, sorbitol, D-glycero-D-galactoheptose, D-glycero-D-glucoheptose, D-glycero-D-mannoheptose, D-glycero-L-mannoheptose, D-altroheptulose, D-mannoheptulose, D-altro-3-heptulose, D-glycero-D-galaheptitol, D-erythro-D-galaoctitol, D-glycero-D-mannooctulose, D-erythlo-L-glononulose, celloblose, maltose, lactose, gentianose, cellotriose and stachyose.

Nonionic Surfactant (B): A compound represented by the formula: RCOO(AO)_(m)R′ (wherein R represents an alkyl or alkenyl group having 7 to 23 carbon atoms; R′ represents a hydrogen atom, an alkyl group having 1 to 22 carbon atoms, an alkenyl group having 2 to 22 carbon atoms, or an acyl group having 2 to 22 carbon atoms; AO represents an oxyalkylene group having 2 to 4 carbon atoms; and m is an integer of 1 or more).

When the carbon atom number of the alkyl or alkenyl group in the definition of R is 7 to 23, nonionic surfactant (B) exhibits an excellent ink-collecting ability and an excellent ink-liberating ability to thereby provide reclaimed pulp having a high whiteness and an excellent appearance.

When the carbon atom number of the alkyl, alkenyl or acyl group in the definition of R′ is 22 or less, or R′ represents a hydrogen atom, nonionic surfactant (B) exhibits an excellent ability for liberating ink from cellulose to thereby provide reclaimed pulp having an excellent appearance, and exhibits an appropriate lathering power to thereby attain an excellent workability.

Nonionic surfactant (B) is produced by adding an alkylene oxide to a fatty acid by a conventional method, optionally followed by esterification or acylation. The alkylene oxide is added to a fatty acid in an amount, on the average, of 5 to 300 moles, preferably 10 to 150 moles, per mole of the fatty acid. That is, nonionic surfactant (B) is generally a reaction product mixture comprising compounds each represented by the above formula: RCOO(AO)_(m)R′. Examples of the alkylene oxides include those described in the above explanation relating to nonionic surfactant (A). It is preferred to use ethylene oxide and propylene oxide in a molar ratio of ethylene oxide to propylene oxide of 1/5 to 5/1 in the production of nonionic surfactant (B).

Examples of the fatty acids to be used for producing nonionic surfactant (B) include those having an alkyl or alkenyl moiety, corresponding to R, of 7 to 23 carbon atoms, and specific examples thereof include caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, stearolic acid, ricinolic acid, ricinoelaidic acid, nonadecanoic acid, arachidic acid, heneicosanoic acid, behenic acid, brassidic acid, erucic acid, tricosanoic acid, tetracosanoic acid, coconut oil fatty acid, beef tallow fatty acid, palm oil fatty acid, tall oil fatty acid, rape oil fatty acid and fish oil fatty acid. Among nonionic surfactants (B), those having an alkyl or alkenyl group represented by R of 11 to 23 carbon atoms are preferred.

Nonionic surfactant (C): A compound represented by the formula: RO(AO)_(n)H (wherein R represents an alkyl or alkenyl group having 8 to 24 carbon atoms; AO represents an oxyalkylene group having 2 to 4 carbon atoms; and n is an integer of 1 or more).

When the carbon atom number of the alkyl or alkenyl group in the definition of R is 8 to 24, nonionic surfactant (C) exhibits an excellent ability for liberating ink from cellulose to thereby provide reclaimed pulp having a high whiteness and an excellent appearance.

Nonionic surfactant (C) is produced by adding an alkylene oxide to a monohydric alcohol by a conventional method. The alkylene oxide is added to a monohydric alcohol in an amount, on the average, of 5 to 300 moles, preferably 7 to 150 moles, per mole of the monohydric alcohol. That is, nonionic surfactant (C) is generally a reaction product mixture comprising compounds each represented by the above formula: RO(AO)_(n)H. Examples of the alkylene oxides include those described in the above explanation relating to nonionic surfactant (A). It is preferred to use ethylene oxide and propylene oxide in a molar ratio of ethylene oxide to propylene oxide of 1/5 to 5/1 in the production of nonionic surfactant (C).

Examples of the monohydric alcohols to be used for producing nonionic surfactant (C) include those having an alkyl or alkenyl moiety of 8 to 24 carbon atoms and those having an alkylphenyl moiety wherein the alkyl moiety has 6 to 14 carbon atoms, and specific examples thereof include those described in the above explanation relating to nonionic surfactant (A). Among nonionic surfactants (C), those having an alkyl or alkenyl group represented by R of 14 to 24 carbon atoms are preferred.

Nonionic surfactant (D): A reaction product obtained by adding an alkylene oxide to a polyvalent carboxylic acid or an acid anhydride thereof; or a reaction product obtained by adding an alkylene oxide to a mixture of a polyvalent carboxylic acid or an acid anhydride thereof, and alcohol.

Examples of the polyvalent (or polybasic) carboxylic acids and acid anhydride thereof as a raw material of nonionic surfactant (D) include oxalic acid, malonic acid, succinic acid, methylsuccinic acid, maleic acid, glutaric acid, adipic acid, phthalic acid, fumaric acid, itaconic acid, malic acid, tartaric acid, maleated oleic acid, citric acid, percitric acid, trimellitic acid, butanetetracarboxylic acid, pyromellitic acid, tetradecanehexacarboxylic acid, maleic anhydride, succinic anhydride, oxalic anhydride, itaconic anhydride, glutaric anhydride, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride and stearylsuccinic anhydride.

Further, dimer acids and polymer acids of higher fatty acids having 14 to 22 carbon atoms are included in the scope of the polyvalent carboxylic acid. Dimer acids and polymer acids herein can be synthesized by a method wherein a monoolefinic carboxylic acid or a diolefinic carboxylic acid, such as an unsaturated fatty acid monomer, e.g., oleic acid, linoleic acid or linolenic acid, is subjected to thermal polymerization such as a Diels-Alder reaction, or another method. The polymer acid herein is a polycarboxylic acid having three or more carboxyl groups in a molecule and does not includes a dimer acid. The dimer acid or polymer acid used herein may be a mixture thereof with an unreacted monomer acid. That is, it is not concerned that an unreacted monomer acid is present as far as the effects of the present invention are not failed.

Examples of the alcohols as a raw material of nonionic surfactant (D) include monohydric alcohols and polyhydric alcohols, and specific examples thereof include those described in the above explanation relating to nonionic surfactant (A).

In the production of nonionic surfactant (D) with a polyvalent carboxylic acid or an acid anhydride thereof (I) and an alcohol (II), the compounds (I) and (II) are preferably used in a molar ratio of (I) to (II) of 1/0.02 to 5/1, particularly 1/0.1 to 3/1. When the molar ratio falls within this range, the above-mentioned nonionic surfactant (D) can efficiently collect fine ink drops and the collected ink drops are effectively removed out from the system in flotation. Therefore, a reclaimed pulp having a high whiteness is provided.

The nonionic surfactant may be added in any step of the deinking process. However, it is usually added in a pulping step. The addition amount thereof is not specifically restricted. A sufficient ink-liberating effect is not achieved with only a deinking agent other than these nonionic surfactants of the present invention. A known deinking agent other than nonionic surfactants (A) to (D) described above may be used in combination therewith.

The flotation method as one of deinking methods is characterized in that a pulp/water slurry is lathered by a suitable means such as a physical means and a chemical means, ink drops adhere to floated foams and the resulting foams with ink drops are rejected to thereby separate ink from pulp. In the deinking method of the present invention, at least part of the flotation step is effected at a pH in a range of from 4 to 9, preferably from 6 to 8. Therefore, the pH of the pulp/water slurry may be adjusted at a pH in a range of from pH4 to pH9 in any step before flotation.

The steps prior to flotaion are effected generally at a basic pH. Therefore, in the present invention, a suitable acid or an aqueous solution thereof is added to the pulp/water slurry before or during flotation to adjust the pH of the slurry to a value in the above-mentioned range. An acid or an aqueous solution thereof may be added to the water which is poured into the slurry before or during flotation, though the addition method of the acid is not specifically restricted. Examples of the acids to be used for adjusting the pH of the slurry include inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid, salts thereof, and organic acids such as acetic acid, formic acid and citric acid. The method for adjusting the pH of the slurry is not restricted to those using acids. When the pH of the slurry in at least part of the flotation step is a value within the range described above, an increase in whiteness of the reclaimed pulp, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery are attained. Further, apparatuses and pulp fibers per se are affected by the properties of the slurry.

The deinking method of the present invention is also characterized in that a cationic compound, an amine, an acid salt of an amine or an amphoteric conpound is to be present in the system in flotation.

The cationic compound herein is cationic or has a cationic group at pH 4 to 9 in flotation. Examples of the cationic compounds include mono(long-chain)alkyl-type quaternary ammonium salts, di(long-chain)alkyl-type quaternary ammonium salts, pyridinium salts having a substituent at the nitrogen atom thereof, and cationic polymers. In particular, the compounds represented by the above formulas (a₁) to (e₁) and cationic polymers represented by the above formulas (f₁) to (j₁) each of which has a cationic nitrogen content of 0.01 to 35% by weight and a weight-average molecular weight of 2,000 to 3,000,000 are preferred.

In the respective formulas (a₁) to (e₁), examples of the groups in the definitions of R₁ and R₂ include lauryl group, myristyl group, cetyl group, stearyl group, behenyl group, oleyl group and linoleyl group. R₁ and R₂ may be the same or different from each other. Examples of the alkyl groups each having 1 to 8 carbon atoms in the definitions of R₃, R₄ and R₅ include methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group, isopropyl group and isobutyl group. R₃, R₄ and R₅ may be the same or different from one another. Examples of the acyl groups in the definition of Z include those derived from fatty acids each having 2 to 24 carbon atoms, e.g., formyl group, acetyl group, propionyl group, butyryl group, lauroyl group, myristoyl group, palmitoyl group, stearoyl group, isobutyryl group, oleoyl group and methacryl group. Examples of the groups in the definition of R₆ include octyl group, lauryl group, myristyl group, cetyl group, stearyl group, behenyl group, hexacosyl group, hexatriacontyl group, oleyl group and linolenyl group. X⁻ is a counter ion and examples thereof include a hydroxyl ion, halide ions, monoalkylsulfate ions wherein the alkyl portion has 1 to 3 carbon atoms, and anions derived from inorganic and organic acids. Specially, X⁻ represents a halide ion such as a chloride ion, a bromide ion and a fluoride ion, a monoalkylsulfate ion such as a methylsulfate ion and an ethylsulfate ion, a counter ion derived from an inorganic acid such as sulfuric acid, nitric acid, carbonic acid and phosphoric acid, or another counter ion derived from a mono- or polyvalent organic acid such as acetic acid and citric acid.

The cationic polymers represented by the above formulas (f₁) to (j₁) each has a weight-average molecular weight of 2,000 to 3,000,000, preferably 10,000 to 1,000,000 and contains 0.01 to 35% by weight, preferably 0.01 to 10% by weight, still more preferably 0.1 to 5% by weight, of cationic nitrogen atoms. The cationic nitrogen content is determined, for example, by determining the nitrogen content (%) of the polymer by Kjeldahl method and multiplying the nitrogen content (%) determined by the ratio of the cationic nitrogen to the total nitrogen which is calculated from the molucular formula of the polymer.

Examples of the above-mentioned cationic polymers include polymers comprising acrylamide and modified with a group having a quaternary ammoniun group, such as acrylamide polymers modified with a group having a quaternary ammoniun group and copolymers of acrylamide with an acrylate modified with a group having a quaternary ammoniun group; polymers comprising an acrylate and modified with a group having a quaternary ammoniun group, such as acrylate polymers modified with a group having a quaternary ammoniun group and copolymers of an acrylate with the other acrylate modified with a group having a quaternary ammoniun group; stylene polymers modified with a group having a quaternary ammoniun group; diallylamine polymers modified with a group having a quaternary ammoniun group; cationized cellulose; and cationed chitosan.

In the respective formulas (f₁) to (j₁), examples of the groups in the definitions of R₁, R₂, R₃, R₆, R₇, R₈ and R₉ include methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group, lauryl group, myristyl group, cetyl group, stearyl group, behenyl group, oleyl group, linoleyl group, isopropyl group and isobutyl group. X⁻ and W⁻ in the above formulas (f₁) to (j₁) are each a counter ion and examples thereof include those described in the above explanation relating to X⁻ in formulas (a₁) to (e₁). Further, the AO in the above formulas (f₁) to (j₁) refers to an oxyalkylene group having 2 to 4 carbon atoms, and examples thereof include oxyethylene group, oxypropylene group and oxybutylene group.

The amine or the acid salt of the amine herein has a nitrogen atom which may be cationized at pH 4 to 9 in flotation. Examples of the amines and the acid salts of amines include primary amines, secondary amines, tertiary amines, cyclic amines, imidazoles and imidazolines; inorganic acid salts of these amines; organic acid salts of these amines; and polymers having an amino group. In particular, the compounds represented by the above formulas (a₂) to (h₂) and polymers represented by the above formulas (i₂) to (l₂) each of which has an amino-nitrogen content of 0.01 to 35% by weight and a weight-average molecular weight of 2,000 to 3,000,000 are preferred.

In the respective formulas (a₂) to (h₂), examples of the groups in the definition of R₁ include those described in the above explanation relating to R₆ in formulas (a₁) to (e₁). Examples of the groups in the definitions of R₂ and R₃ include those described in the above explanation relating to R₁, R₂, R₃, R₆, R₇, R₈ and R₉ in formulas (f₁) to (j₁). R₂ and R₃ may be the same or different from each other. HA represents an inorganic acid, e.g., hydrochloric acid, sulfuric acid, nitric acid, carbonic acid, phosphoric acid or hydrobromic acid; or a mono- or polyvalent organic acid, e.g., formic acid, acetic acid, propionic acid, butyric acid, lauric acid, stearic acid, malonic acid, succinic acid, acrylic acid, maleic acid, fumaric acid or citric acid. l and m are each zero or a positive integer with the proviso that l plus m is an integer of 1 to 300. Examples of the alkyl groups in the definitions of W₁, W₂, W₃ and W₄ include methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group, lauryl group, myristyl group, cetyl group, stearyl group, behenyl group, isopropyl group and isobutyl group. W₁, W₂, W₃ and W₄ may be the same or different from one another.

Among amines and acid salts of amines represented by the above formulas (a₂) to (h₂), preferred are those represented by the formulas (a₂) to (h₂) wherein R₁ represents an alkyl, alkenyl or β-hydroxyalkyl group having 8 to 36 carbon atoms; R₂ and R₃ may be the same or different from each other and each represents a hydrogen atom or an alkyl group having 1 to 24 carbon atoms; HA represents an inorganic or organic acid; AO represents an oxyalkylene group having 2 to 4 carbon atoms; l and m are each such an integer that l plus m would be a numerical value of above zero and 300 or below; and W₁, W₂, W₃ and W₄ may be the same or different from one another and each represents a hydrogen atom or an alkyl group having 1 to 24 carbon atoms.

The polymers represented by the above formulas (i₂) to (l₂) each has a weight-average molecular weight of 2,000 to 3,000,000, preferably 10,000 to 1,000,000 and contains 0.01 to 35% by weight, preferably 0.01 to 10% by weight, still more preferably 0.1 to 5% by weight, of amino-nitrogen atoms. The amino-nitrogen content is determined, for example, by determining the nitrogen content (%) of the polymer by KJeldahl method and multiplying the nitrogen content (%) determined by the ratio of the amino-nitrogen to the total nitrogen which is calculated from the molucular formula of the polymer.

Examples of the above-mentioned polymers include linear polyamines such as polyvinylamine and polyethyleneimine; polymers of cyclic amines such as polyvinylpyridine, polyaminostyrene and polyvinylimidazole; formaldehyde condensates such as melamine/formaldehyde condensate and urea/formaldehyde condensate; polymers comprising acrylamide and modified with a group having an amino group, such as acrylamide polymers modified with a group having an amino group and copolymers of acrylamide with an acrylate modified with a group having an amino group; polymers comprising an acrylate and modified with a group having an amino group, such as acrylate polymers modified with a group having an amino group and copolymers of an acrylate with the other acrylate modified with a group having an amino group; and polymeric amine compounds such as chitosan; and acid salts of these polymers.

In the respective formulas (i2) to (l₂), examples of the alkyl groups and alkenyl groups in the definitions of R₁, R₂, R₃ and R₆ include methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group, lauryl group, myristyl group, cetyl group, stearyl group, behenyl group, oleyl group, linoleyl group, isopropyl group and isobutyl group. HA represents an inorganic or oragnic acid, and examples thereof include those described in the above explanation relating to HA in formulas (a₂) to (h₂).

The amphoteric compound herein has a cationic group at pH 4 to 9 in flotation. Examples of the amphoteric compounds include betaines, amine oxides, phospholipids, proteins and amphoteric polymers. In particular, the compounds represented by the above formulas (a₃) to (j₃), phospholipids (k₃), proteins (l₃) and amphoteric polymers represented by the above formulas (m₃) and (n₃) each of which has a cationic nitrogen content of 0.01 to 35% by weight and a weight-average molecular weight of 2,000 to 3,000,000 are preferred. Further, proteins (l₃) each having a weight-average molecular weight of 2,000 to 3,000,000, desirably 10,000 to 1,000,000 and containing 0.01 to 35% by weight, desirably 0.01 to 10% by weight, still more desirably 0.1 to 5% by weight, of cationic nitrogen atoms, are still more preferred.

In the respective formulas (a₃) to (j₃), examples of the alkyl groups and alkenyl groups in the definitions of R₁, R₂ and R₃ include those described in the above explanation relating to R₁, R₂, R₃ and R₆ in formulas (i₂) to (l₂). Examples of the groups in the definitions of R₄ include those described in the above explanation relating to R₆ in formulas (a₁) to (e₁). Examples of the groups in the definitions of R₅ include methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group, isopropyl group, isobutyl group, lauryl group, myristyl group, cetyl group, stearyl group, behenyl group, hexacosyl group, hexatriacontyl group, oleyl group and linoleyl group.

Examples of the phospholipids (k₃) include phosphatidyl choline, phosphatidyl ethanolamine, sphingomyelin, phosphatidyl serine and lysolecithine. Further, examples of the proteins (l₃) include natural proteins derived from natural materials, e.g., soybean protein or lactoprotein, those prepared by the partial hydrolysis of the natural proteins, and denatured products of the natural proteins. The molecular weight, kind of the atoms constituting the protein, the degree of the denaturation or the like is not restricted.

Among amphoteric compounds represented by the above formulas (a₃) to (j₃), phospholipids (k₃) and proteins (l₃), preferred are phospholipids. (k₃), proteins (l₃) and those represented by the formulas (a₃) to (j₃) wherein R₁, R₂ and R₃ may be the same or different from one another and each represents an alkyl group having 1 to 24 carbon atoms; R₄ represents an alkyl, alkenyl or β-hydroxyalkyl group having 8 to 36 carbon atoms; M represents a hydrogen atom, an alkali metal atom, ½ mole of an alkaline earth metal atom or an ammonium group; Y₁ represents a group represented by the formula: R₅NHCH₂CH₂— (wherein R₅ represents an alkyl, alkenyl or β-hydroxyalkyl group having 8 to 36 carbon atoms); Y₂ represents a hydrogen atom or a group represented by the formula: R₅NHCH₂CH₂— (wherein R₅ is as defined above); Z₁ represents a group represented by the formula: —CH₂COOM (wherein M is as defined above); and Z₂ represents a hydrogen atom or a group represented by the formula: —CH₂COOM (wherein M is as defined above).

The amphoteric polymers other than proteins, and represented by the above formulas (m₃) and (n₃) each has a weight-average molecular weight of 2,000 to 3,000,000, preferably 10,000 to 1,000,000 and contains 0.01 to 35% by weight, preferably 0.01 to 10% by weight, still more preferably 0.1 to 5% by weight, of cationic nitrogen atoms. The cationic nitrogen content is determined, for example, by determining the nitrogen content (%) of the polymer by Kjeldahl method and multiplying the nitrogen content (%) determined by the ratio of the cationic nitrogen to the total nitrogen which is calculated from the molucular formula of the polymer.

Examples of the above-mentioned amphoteric polymers include polyvinylbetaines, copolymers of acrylic acid with acrylamide partially modified by Mannich reaction, and copolymers of an dialkylaminoalkyl acrylate with a sulfonated stylene.

In the respective formulas (m₃) and (n₃), examples of the alkyl groups and alkenyl groups in the definitions of R₁, R₂ and R₃ include those described in the above explanation relating to R₁, R₂, R₃, R₆, R₇, R₈ and R₉ in formulas (f₁) to (j₁). R₁, R₂ and R₃ may be the same or different from one another.

At least one member selected from the group consisting of cationic compounds, amines, acid salts of amines and amphoteric compounds is used in an amount of 0.001 to 5.0% by weight, preferably 0.01 to 1.0% by weight, based on the weight of waste paper (i.e., the absoluted dry weight of waste paper) in flotaion. When the above-mentioned at least one member selected is present in the system, i.e., in the slurry, in flotation in such an amount as described above, ink can be selectively removed from the system.

In the present invention, it is necessary that a pulp/water slurry in at least one step of flotation contains the cationic compound, amine, acid salt of amine or amphoteric compound. Therefore, the cationic compound, amine, acid salt of amine or amphoteric compound may be added at any of the steps of the deinking process, as long as the step is not one to be effected after flotation. It may be added in a step before flotation, for example, a disintegration step or a bleaching step, or alternatively added just before flotaion or during flotation (e.g., in an early stage of the flotation step). Preferably, the cationic compound, amine, acid salt of amine or amphoteric compound is added to the slurry just before flotaion or during flotation, and after adjusting the pH of the slurry to a value in a range of from 4 to 9. In this case, the cationic compound, amine, acid salt of amine or amphoteric compound is preferably used in such an amount that the pH of the system for flotation is scarcely altered by the addition thereof. “The pH of the system for flotation is scarcely altered” refers that the alteration of the pH of the system is not recognized or recognized only in two places of decimals in the determination of pH. The amount of the cationic compound, amine, acid salt of amine or amphoteric compound that the pH of the flotation system is scarcely altered by the addition thereof is, e.g., from 0.01 to 1.0% by weight based on the weight (i.e., the absoluted dry weight) of waste paper.

The flotation step may comprise two or more steps when, for example, the flotation system is circulated. In such a case, the pH of the system has to be regulated to a value in a range of from 4 to 9 at least one flotation step. It is preferred that the pH of the system in the step, among steps of flotation, immediately before the washing step is regulated as described above. At least one member selected from the group consisting of cationic compounds, amines, acid salts of amines and amphoteric compounds also has to be present in the system having a pH of from 4 to 9 in at least one step of flotation.

In the deinking method of the present invention, the calcium ion concentration of the system, i.e., the slurry, in flotation is not specifically restricted. In order to obtain a reclaimed pulp having a higher quality, however, the calcium ion concentration of the system in flotation is preferably controlled to a value in the range of from 10 to 400 ppm, particularly from 100 to 250 ppm. When the calcium ion concentration falls within the above-mentioned range, fine drops of ink can be selectively flocculated one another to give ink drops having an optimum size for flotation reject. Therefore, ink is easily rejected by foltaion to give a reclaimed pulp having a higher whiteness and a less residual ink spots.

For the regulation of the calcium ion concentration of the system, inorganic calcium salts such as calcium chloride and calcium carbonate, and minerals such as lime can be used. Further, an animal bone, a shell or the like may be used as the sourse of the calcium ion. In such a case, the animal bone or the like is reacted with an acid to thereby ionize. Although the calcium ion concentration of the system in flotation is preferably regulated to a value in the above-mentioned range, the calcium ion concentration of the system in any step other than the flotation step is not restricted. Therefore, the calcium ion concentration of the system may be adjusted in any step (such as the pulping step) prior to the flotation step, as far as the liberation of ink is not affected.

In the deinking method of the present invention, the aluminum ion concentration of the system in flotation is desirably regulated to 40 ppm or less, particularly 25 ppm or less. For the regulation of the aluminum ion concentration of the system, it is preferred to take the kind and amount of water used in flotation into consideration. For example, white water resulting from paper-making and/or city water are used in a suitable amount. When the aluminum ion concentration of the system in flotation is regulated as described above, not only both an improvement in the whiteness of the reclaimed pulp and a decrease of the residual ink spots of the reclaimed paper are achieved, but also the recovery of pulp is enhanced. Although the aluminum ion concentration of the system in flotation is preferably regulated to a value in the above-mentioned range, the aluminum ion concentration of the system in any step other than the flotation step is not restricted. Therefore, the aluminum ion concentration of the system may be adjusted in any step (such as the pulping step) prior to the flotation step, as far as the liberation of ink is not affected.

The deinking method of the present invention described above is characterized in that at least one of nonionic surfactants (A) to (D) is used, and that at least part of the flotation step is effected in the presence of at least one member selected from the group consisting of cationic compounds, amines, acid salts of amines and amphoteric compounds at a pH in a range of from 4 to 9; and comprises at least steps of liberating ink from waste paper and removing the liberated ink from a flotation system. Other steps can be carried out according to the conventional deinking method. That is, the deinking method may comprise, as the main steps, a disintegrating (or pulping) step, an aging step, (a kneading step, if necessary), a flotation step and a washing step. The deinking method may further comprise other step(s), if necessary. The respective steps may be carried out two or more times.

According to the present invention, deinked pulp having a higher whiteness and a less residual ink spots can be obtained from waste paper as the raw material. Therefore, it becomes possible to reduce the production cost of the deinked pulp since bleaching chemicals such as caustic soda, sodium silicate, hydrogen peroxide and chelating agents are necessitated in only small amounts. and the recovery of pulp is increased.

Although the mechanism why the deinking method of the present invention exhibits such an excellent deinking effect is not necessarily clarified, it is considered as follows:

That is, ink is sufficiently liberated from pulp by using a nonionic surfactant as the deinking agent and, further, the reduction of the pH of the system before or during flotation brings about an alteration in conditions of the interface between pulp and ink to cause existing a cationic compound, an amine, an acid salt of an amine or an amphoteric compound to adsorb preferentially on the ink, thereby aggregating ink by the cohesion of the cationic compounds (amines, acid salts of amines or amphoteric compounds) therebetween at their hydrophobic portions. In this case, the presence of the nonionic surfactant in the system prevents the re-adhesion of ink to pulp. When the nonionic surfactant is not present in the system, the cationic compound or the like adsorbs on both ink and pulp, which results in causing the re-adhesion of ink to the pulp.

In any event, there are essentials in the deinking method of the present invention that (1) a nonionic surfactant is used as a deinking agent, (2) the pH of the system is regulated to a low value in the presence of the above nonionic surfactant, and (3) aggregation of ink is carried out with a cationic compound, an amine, an acid salt of an amine or an amphoteric compound.

EXAMPLES

The present invention will be described in detail with reference to the following Examples which should not be considered to limit the present invention.

<Cationic Compounds>

The cationic compounds used in the following Examples I-1 to I-10 will be shown in the following Tables I-1 to I-5.

In Tables I-1 to I-5, each numeral in the columns of R₁ to R₆, R_(6a) and R_(6b) means the carbon atom number of a linear alkyl group as a substituent; and “18 F1”, “18 Hyd” and “12 Hyd” refer oleyl group, β-hydroxystearyl group and β-hydroxylauryl group, respectively.

Further, in the following Examples, “EO” and “PO” refer oxyethylene group and oxypropylene group, respectively; and the subscript refers an average molar number of ethylene oxide or propylene oxide added.

TABLE I-1 Compd. Substituent and counter ion General formula No. R₁ R₂ R₃ R₄ X⁻

a₁-1 a₁-2 a₁-3 a₁-4 a₁-5 a₁-6 a₁-7 a₁-8 10 12 12 12 18 18 18 18 F1 24 12 18 12 18 18 18 Hyd 18 F1 1 1 1 8 2 # 4 2 2 1 2 1 8 2 4 2 2 Cl⁻ Br⁻ CH₃COO⁻ 1/2 SO₄ ²⁻ Cl⁻ Cl⁻ Cl⁻ Cl⁻

TABLE I-2 Compd. Substituent and counter ion General formula No. R₃ R₄ R₅ R₆ X⁻

b₁-1 b₁-2 b₁-3 b₁-4 b₁-5 b₁-6 b₁-7 b₁-8 b₁-9 b₁-10 b₁-11 b₁-12 1 1 1 1 4 1 2 1 1 1 1 1 (EO)₂₀-H #1 1 1 4 1 2 1 1 1 1 1 (EO)₂₀-H (EO)₂₀-H 1 8 1 4 benzyl 2 1 1 1 (EO)₅₀-H (EO)₅₀-H (EO)₅₀-H 12 12 18 18 18 22 # 34 12 Hyd 18 F1 18 18 18 Cl⁻ Br⁻ CH₃COO⁻ 1/2 SO₄ ²⁻ Cl⁻ Cl⁻ Cl⁻ Cl⁻ Cl⁻ Cl⁻ Cl⁻ Cl⁻

TABLE I-3 Substituent and Compound counter ion General formula No. Y X⁻

c₁-1 c₁-2 c₁-3 c₁-4 C₈H₁₇COOCH₂ C₁₂H₂₅CONHCH₂ C₁₈H₃₇OCH₂ C₁₂H₂₅ Cl⁻ Cl⁻ Br⁻ Br⁻

TABLE I-4 Substituent and Compound counter ion General formula No. R₃ R₆ X⁻

d₁-1 d₁-2 d₁-3 1 4 8 12 18 F1 22 Cl⁻ Cl⁻ Br⁻

TABLE I-5 Substituent and Compound counter ion General formula No. R_(6a) R_(6b) X⁻

e₁-1 e₁-2 e₁-3 12 18 12 12 18 F1 22 Cl⁻ Cl⁻ Br⁻

Example I-1

Waste papers (news papers/leaflets=75/25) recovered in a city were cut into pieces (2×5 cm). A given amount thereof was fed into a bench disintegrator. Then, warm water, 1% by weight (based on the waste papers) of caustic soda, 3% by weight (based on the waste papers) of sodium silicate, 3% by weight (based on the waste papers) of 30% by weight aqueous solution of hydrogen peroxide and 0.2% by weight (based on the waste papers) of an EO₁₀/PO₁₀ block adduct of stearyl alcohol as a deinking agent were added thereto to prepare a mixture. The waste papers in the mixture were disintegrated at 40° C. for 10 minutes to prepare a pulp slurry having a pulp concentration of 5% by weight. The resulting pulp slurry was maintained at 40° C. for 60 minutes, and then warm water was added to the pulp slurry. Thus, a pulp slurry having a pulp concentration of 1% by weight was prepared. Hydrochloric acid was added to the pulp slurry to adjust the pH thereof to a value shown in Table I-6. To the pulp slurry, a cationic compound shown in Table I-1 or I-2, and Table I-6 was further added in an amount shown in Table I-6. By the addition of the cationic compound, the pH of the resulting pulp slurry was scarcely altered. After sampling from the resulting pulp slurry (before flotation), the pulp slurry was subjected to flotation at 40° C. for 10 minutes to prepare a pulp slurry (after flotation).

The whitenesses of the pulp sheet prepared from the pulp slurry (before flotation) and the pulp slurry (after flotation) were measured. The residual ink area ratio of the pulp sheet obtained from the pulp slurry (after flotation) was also measured. Specially, aluminum sulfate was added to each of the pulp slurry (before flotation) and the pulp slurry (after flotation) to adjust the pH thereof to 5, and the resulting pulp slurries were each treated on a TAPPI standard sheet machine to give pulp sheet. The pulp sheet thus obtained were dried under airing. The whitenesses of the resulting pulp sheet were determined with a color-difference meter, and the residual ink area ratio of the pulp sheet obtained from the pulp slurry (after flotation) was determined with an image analyzer (magnification:×100).

An increase by 1% in the whiteness of the pulp sheet and a reduction by 0.1% in the residual ink area ratio thereof can be recognized with naked eyes such that the quality of the pulp sheet was sufficiently improved.

The recovery of pulp in flotation was determined from the absolute dry weight of the pulp contained in the pulp slurry before flotation and the absolute dry weight of the pulp contained in flotation reject [i.e., [(the absolute dry weight of the pulp contained in the pulp slurry before flotation)—(the absolute dry weight of the pulp contained in flotation reject)] ×100/(the absolute dry weight of the pulp contained in the pulp slurry before flotation)]. The results thereof are shown in Table I-6.

TABLE I-6 Residual Reco- ink area very Cationic compound pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%)  1 None — 10.0 45.0 52.2 0.752 86.8  2 None — 9.0 45.4 52.8 0.683 87.2  3 None — 8.0 44.9 53.3 0.411 88.3  4 None — 7.0 45.6 53.6 0.365 88.9  5 None — 6.0 45.0 54.0 0.329 88.9  6 None — 5.0 44.6 53.1 0.431 89.1  7 None — 4.0 44.3 52.9 0.625 87.6  8 a₁-4 0.10 9.0 45.0 55.7 0.252 89.2  9 a₁-4 0.10 8.0 44.8 57.4 0.151 89.0 10 a₁-4 0.10 7.0 44.6 57.2 0.149 93.1 11 a₁-4 0.10 6.0 44.7 56.8 0.179 92.5 12 a₁-4 0.10 5.0 44.3 56.6 0.221 92.7 13 b₁-1 0.10 4.0 44.3 56.0 0.239 91.3 14 b₁-1 0.06 9.0 45.5 55.9 0.247 88.9 15 b₁-1 0.06 8.0 45.0 57.7 0.147 88.8 16 b₁-1 0.06 7.0 45.1 57.4 0.146 93.0 17 b₁-1 0.06 6.0 44.9 57.1 0.167 92.3 18 b₁-1 0.06 5.0 44.8 56.9 0.215 92.4 19 b₁-1 0.06 4.0 44.2 56.3 0.243 91.3 20 b₁-11 0.03 9.0 45.1 55.8 0.242 87.8 21 b₁-11 0.03 8.0 45.0 58.0 0.136 87.4 22 b₁-11 0.03 7.0 44.7 57.7 0.144 91.3 23 b₁-11 0.03 6.0 44.7 57.4 0.150 90.7 24 b₁-11 0.03 5.0 44.5 56.8 0.199 91.2 25 b₁-11 0.03 4.0 44.3 56.2 0.215 89.9

In the Tests described above, Test No. 1 is effected in a similar manner as that of a conventional industrial deinking method. According to the methods of Test Nos. 8 to 25 (the methods of the present invention) wherein the flotation is effected in the presence of a cationic compound at a specific pH, as compared with those of Test Nos. 1 to 7 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

Example I-2

Deinking test was carried out according to the method described in Example I-1 by using cationic compounds shown in Tables I-1 and I-7. The result are shown in Table I-7.

TABLE I-7 Residual Reco- ink area very Cationic compound pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 26 None — 10.0 45.1 52.3 0.749 86.8 27 None — 7.0 45.3 54.6 0.431 88.8 28 a₁-1 0.10 7.0 45.2 57.4 0.144 92.3 29 a₁-2 0.10 7.0 45.0 57.2 0.151 92.2 30 a₁-3 0.10 7.0 45.2 57.2 0.148 92.1 31 a₁-4 0.10 7.0 44.6 57.2 0.155 93.3 32 a₁-5 0.10 7.0 45.2 57.4 0.148 92.7 33 a₁-6 0.10 7.0 45.2 57.6 0.147 93.4 34 a₁-7 0.10 7.0 45.2 57.4 0.142 92.0 35 a₁-8 0.10 7.0 45.1 57.3 0.146 92.7

According to the methods of Test Nos. 28 to 35 (the methods of the present invention) wherein the flotation is effected in the presence of a cationic compound shown in Table I-1 at a specific pH, as compared with those of Test Nos. 26 and 27 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

Example I-3

Deinking test was carried out according to the method described in Example I-1 by using cationic compounds shown in Tables I-2 and I-8. The results are shown in Table I-8.

TABLE I-8 Residual Reco- ink area very Cationic compound pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 36 None — 10.0 45.0 52.3 0.744 86.9 37 None — 7.0 45.2 54.3 0.446 88.8 38 b₁-1 0.10 7.0 45.1 57.2 0.157 91.7 39 b₁-2 0.10 7.0 45.1 57.8 0.143 92.4 40 b₁-3 0.10 7.0 45.0 58.0 0.101 92.6 41 b₁-3 0.10 7.0 44.9 57.3 0.145 92.7 42 b₁-5 0.10 7.0 44.8 57.6 0.143 92.1 43 b₁-6 0.10 7.0 45.0 57.0 0.165 92.8 44 b₁-7 0.10 7.0 45.2 58.0 0.137 93.2 45 b₁-8 0.10 7.0 45.4 57.5 0.148 92.3 46 b₁-9 0.10 7.0 45.3 57.7 0.146 92.9 47 b₁-10 0.10 7.0 45.2 57.2 0.151 91.6 48 b₁-11 0.10 7.0 45.0 57.6 0.143 91.4 49 b₁-12 0.05 7.0 45.0 57.1 0.156 92.3 50 b₁-12 0.10 7.0 45.0 57.9 0.135 91.9 51 b₁-12 0.20 7.0 45.1 59.2 0.123 91.0

According to the methods of Test Nos. 38 to 51 (the methods of the present invention) wherein the flotation is effected in the presence of a cationic compound shown in Table I-2 at a specific pH, as compared with those of Test Nos. 36 and 37 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

Example I-4

Deinking test was carried out according to the method described in Example I-1 by using cationic compounds shown in Tables I-3 and I-9. An EO₂₀ adduct pf stearic acid was used as the deinking agent in the present Example. The results are shown in Table I-9.

TABLE I-9 Residual Reco- ink area very Cationic compound pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 52 None — 10.0 45.1 52.0 0.772 86.8 53 None — 7.0 45.4 54.1 0.465 88.2 54 c₁-1 0.05 7.0 45.9 57.3 0.153 92.1 55 c₁-2 0.05 7.0 45.2 56.9 0.158 92.0 56 c₁-3 0.05 7.0 45.1 57.2 0.155 92.1 57 c₁-4 0.05 7.0 45.1 57.6 0.149 91.0

According to the methods of Test Nos. 54 to 57 (the methods of the present invention) wherein the flotation is effected in the presence of a cationic compound shown in Table I-3 at a specific pH, as compared with those of Test Nos. 52 and 53 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

Example I-5

Deinking test was carried out according to the method described in Example I-1 by using cationic compounds shown in Tables I-4 and I-10. An EO₆₀ adduct of a mixture (1:1 by mole) of beef tallow and glycerol was used as the deinking agent in the present Example. The results are shown in Table I-10.

TABLE I-10 Residual Reco- ink area very Cationic compound pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 58 None — 10.0 45.0 51.7 0.704 85.7 59 None — 7.0 45.4 53.8 0.411 86.6 60 d₁-1 0.10 7.0 44.9 57.6 0.142 92.2 61 d₁-2 0.10 7.0 45.3 57.2 0.147 92.4 62 d₁-3 0.10 7.0 45.2 56.9 0.152 92.1

According to the methods of Test Nos. 60 to 62 (the methods of the present invention) wherein the floation is effected in the presence of a cationic compound shown in Table I-4 at a specific pH, as compared with those of Test Nos. 58 and 59 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

Example I-6

Deinking test was carried out according to the method described in Example I-1 by using cationic compounds shown in Tables I-1, I-2 and I-5, and I-11. The results are shown in Table I-11.

TABLE I-11 Residual Reco- ink area very Cationic compound pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 63 None — 10.0 45.1 52.2 0.759 86.8 64 None — 7.0 45.3 54.4 0.434 88,3 65 e₁-1 0.10 7.0 45.1 57.6 0.145 92.1 66 e₁-2 0.10 7.0 45.0 57.4 0.151 92.9 67 e₁-3 0.10 7.0 44.9 56.9 0.153 92.8 68 a₁-2/ 0.05/0.05 7.0 45.3 57.8 0.142 92.5 e₁-1 69 b₁-1/ 0.07/0.03 7.0 45.2 57.7 0.145 92.6 e₁-2

According to the methods of Test Nos. 65 to 69 (the methods of the present invention) wherein the flotation is effected in the presence of a cationic compound shown in Table I-5 optionally together with a cationic compound shown in Table I-1

or I-2 at a specific pH, as compared with those of Test Nos. 63 and 64 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

Example I-7

Waste papers (news papers/leaflets=75/25) recovered in a city were cut into pieces (2×5 cm). A given amount thereof was fed into a disintegrator for a high concentration. Then, warm water, 1% by weight (based on the waste papers) of caustic soda, 3% by weight (based on the waste papers) of sodium silicate, 3% by weight (based on the waste papers) of 30% by weight aqueous solution of hydrogen peroxide and a deinking agent of Table I-12 in an amount given in Table I-13 were added thereto to prepare a mixture. The waste papers in the mixture were disintegrated at 40° C. for 10 minutes to prepare a pulp slurry having a pulp concentration of 15% by weight. Warm water was added to the pulp slurry to prepare a pulp slurry having a pulp concentration of 4% by weight. The resulting pulp slurry was maintained at 40° C. for 60 minutes, and then warm water was added to the pulp slurry. Thus, a pulp slurry having a pulp concentration of 1% by weight was prepared. Sulfuric acid was added to the pulp slurry to adjust the pH thereof to a value shown in Table I-13. To the pulp slurry, a cationic compound shown in Table I-1, I-2 or I-3, and Table I-13 was further added in an amount shown in Table I-13. By the addition of the cationic compound, the pH of the resulting pulp slurry was scarcely altered. After sampling from the resulting pulp slurry (before flotation), the pulp slurry was subjected to flotation at 40° C. for 10 minutes to prepare a pulp slurry (after flotation). The pulp slurries were subjected to paper-making in the same manner as that in Example I-1.

The performances of the pulp sheet thus obtained were evaluated in the same manner as that in Example I-1. The results thereof are shown in Table I-13.

TABLE I-12 Amount added Deinking (based on agent No. Deinking agent waste papers) A1 an EO₁₀/PO₁₀ random adduct 0.2% of stearic acid A2 an EO₃₀/PO₂₅ block adduct of 0.3% dimer acid A3 an EO₇₀/PO₂₀ block adduct of 0.3% a mixture (1:1 by mole) of beef tallow and glycerol A4 Stearic acid 0.5%

TABLE I-13 Amine and acid Residual Reco- Deinking salt of amine ink area very agent No. Amount pH in Whiteness (%) ratio (%) of Test (See Table Compd. added flota- Before After After pulp No. I-12) No. (%) tion flotation flotation flotation (%) 70 A1 None — 10.0 43.9 51.0 0.841 88.5 71 A2 None — 10.0 44.0 52.2 0.785 86.5 72 A3 None — 10.0 44.6 52.1 0.771 86.2 73 A4 None — 10.0 47.8 53.5 0.415 90.0 74 A1 a₁-1 0.10 7.0 44.2 56.3 0.204 92.1 75 A2 a₁-2 0.10 7.0 44.5 57.5 0.155 90.7 76 A3 b₁-6 0.10 7.0 44.6 57.2 0.163 89.9 77 A4 c₁-1 0.05 7.0 47.2 58.6 0.150 93.6

According to the methods of Test Nos. 74 to 77 (the methods of the present invention) wherein various deinking agents are each used and the flotation is effected in the presence of a cationic compound at a specific pH, as compared with those of Test Nos. 70 to 73 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp.

Example I-8

Waste papers (news papers/leaflets=75/25) recovered in a city were cut into pieces (2×5 cm). A given amount thereof was fed into a bench disintegrator. Then, warm water, 1% by weight (based on the waste papers) of caustic soda, 3% by weight (based on the waste papers) of sodium silicate, 3% by weight (based on the waste papers) of 30% by weight aqueous solution of hydrogen peroxide and 0.2% by weight (based on the waste papers) of an EO₁₀/PO₁₀ block adduct of stearyl alcohol as a deinking agent were added thereto to prepare a mixture. The waste papers in the mixture were disintegrated at 40° C. for 10 minutes to prepare a pulp slurry having a pulp concentration of 5% by weight. The resulting pulp slurry was maintained at 40° C. for 60 minutes, and then warm water was added to the pulp slurry to give a pulp slurry having a pulp concentration of 1% by weight and a Ca²⁺ ion concentration given in Table I-14. The Ca²⁺ ion concentration of the warm water had been adjusted with CaCl₂ so as to give the Ca²⁺ ion concentration of the resulting pulp slurry shown in Table I-14. Then, hydrochloric acid was added to the resulting pulp slurry to adjust the pH thereof to a value shown in Table I-14. To the resulting pulp slurry, a cationic compound shown in Table I-1 or I-2, and Table I-14 was further added in an amount shown in Table I-14. By the addition of the cationic compound, the pH of the resulting pulp slurry was scarcely altered. After sampling from the resulting pulp slurry (before flotation), the pulp slurry was subjected to flotation at 40° C. for 10 minutes to prepare a pulp slurry (after flotation). The pulp slurries were subjected to paper-making in the same manner as that in Example I-1.

The performances of the pulp sheet thus obtained were evaluated in the same manner as that in Example I-1. The results thereof are shown in Table I-14.

TABLE I-14 Residual Reco- Cationic compound Ca²⁺ ion ink area very Amount pH in concent- Whiteness (%) ratio (%) of Test Compound added flota- ration Before After After pulp No. No. (%) tion (ppm) flotation flotation flotation (%) 78 None — 10.0 0 44.8 52.1 0.770 86.4 79 None — 10.0 50 45.0 52.2 0.752 86.8 80 None — 10.0 100 45.3 52.5 0.743 87.3 81 None — 10.0 200 45.2 52.6 0.739 87.3 82 None — 10.0 400 45.0 52.3 0.765 87.6 83 None — 10.0 800 44.7 51.8 0.781 87.6 84 b₁-1 0.06 7.0 0 44.8 57.2 0.162 93.5 85 b₁-1 0.06 7.0 50 45.2 57.5 n.145 93.0 86 b₁-1 0.06 7.0 100 45.3 58.4 0.091 92.7 87 b₁-1 0.06 7.0 200 45.6 59.0 0.086 93.0 88 b₁-1 0.06 7.0 400 45.1 57.5 0.128 93.8 89 b₁-1 0.06 7.0 800 45.1 56.4 0.221 94.1 90 a₁-4 0.10 7.0 0 44.3 57.0 0.172 93.4 91 a₁-4 0.10 7.0 200 45.1 58.8 0.092 93.0 92 a₁-4 0.10 7.0 800 45.0 56.2 0.229 93.9 93 b₁-11 0.03 7.0 0 44.3 57.2 0.161 91.9 94 b₁-11 0.03 7.0 200 45.1 59.2 0.085 92.5 95 b₁-11 0.03 7.0 80O 44.6 56.6 0.219 92.7 Note) The Ca²⁺ ion concentrations in the above Table were determined in flotation.

According to the methods of Test Nos. 84 to 95 (the methods of the present invention) wherein the flotation is effected in the presence of a cationic compound at a specific pH at a specific Ca²⁺ ion concentration, as compared with those of Test Nos. 78 to 83 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

Example I-9

Waste papers (news papers/leaflets=75/25) recovered in a city were cut into pieces (2×5 cm). A given amount thereof was fed into a bench disintegrator. Then, warm water, 1% by weight (based on the waste papers) of caustic soda, 3% by weight (based on the waste papers) of sodium silicate, 3% by weight (based on the waste papers) of 30% by weight aqueous solution of hydrogen peroxide and 0.2% by weight (based on the waste papers) of an EO₁₀/PO₁₀ block adduct of stearyl alcohol as a deinking agent were added thereto to prepare a mixture. The waste papers in the mixture were disintegrated at 40° C. for 10 minutes to prepare a pulp slurry having a pulp concentration of 5% by weight. The resulting pulp slurry was maintained at 40° C. for 60 minutes, and then warm water was added to the pulp slurry to give a pulp slurry having a pulp concentration of 1% by weight, an Al³⁺ ion concentration given in Table I-15 and a Ca²⁺ ion concentration given in Table I-15. The Al³⁺ ion concentration of the warm water had been adjusted with white water resulting from paper-making (with white water and aluminum sulfate in Test Nos. 99, 103 and 107) so as to give the Al³⁺ ion concentration of the resulting pulp slurry shown in Table I-15. The Ca²⁺ ion concentration of the warm water had been adjusted with CaCl₂ so as to give the Ca²⁺ ion concentration of the resulting pulp slurry shown in Table I-15. Then, hydrochloric acid or sodium hydroxide was added to the resulting pulp slurry to adjust the pH thereof to a value shown in Table I-15. To the resulting pulp slurry, a cationic compound shown in Table I-1 or I-2, and Table I-15 was further added in an amount shown in Table I-15. By the addition of the cationic compound, the pH of the resulting pulp slurry was scarcely altered. After sampling from the resulting pulp slurry (before flotation), the pulp slurry was subjected to flotation at 40° C. for 10 minutes to prepare a pulp slurry (after flotation). The pulp slurries were subjected to paper-making in the same manner as that in Example I-1.

The performances of the pulp sheet thus obtained were evaluated in the same manner as that in Example I-1. The results thereof are shown in Table I-15.

TABLE I-15 Cationic Residual Reco- compound Al³⁺ Ca²⁺ ink area very Amount pH in ion ion Whiteness (%) ratio (%) of Test Compd. added flota- conc. conc. Before After After pulp No. No. (%) tion (ppm) (ppm) flotation flotation flotation (%)  96 None — 10.0 0 100 45.3 52.5 0.743 87.3  97 None — 10.0 20 100 45.5 52.2 0.776 85.2  98 None — 10.0 40 100 44.4 5i.9 0.802 82.7  99 None — 10.0 60 100 43.4 5l.7 0.822 79.3 100 b₁-1 0.06 7.0 0 100 45.3 58.4 0.091 92.7 101 b₁-1 0.06 7.0 20 100 45.2 57.6 0.126 90.8 102 b₁-1 0.06 7.0 49 100 44.5 56.3 0.232 88.3 103 b₁-1 0.06 7.0 60 100 43.4 53.8 0.497 84.9 104 a₁-4 0.10 7.0 20 100 44.9 57.4 0.132 90.8 105 a₁-4 0.10 7.0 60 100 43.1 53.5 0.533 84.9 106 b₁-11 0.03 7.0 20 100 44.7 57.8 0.125 89.3 107 b₁-11 0.03 7.0 60 100 42.9 53.4 0.526 83.4 Note) The Al³⁺ ion concentrations and the Ca²⁺ ion concentrations in the above Table were determined in flotation.

According to the methods of Test Nos. 100 to 107 (the methods of the present invention) wherein the flotation is effected in the presence of a cationic compound at a specific pH at a specific Ca²⁺ ion concentration, as compared with those of Test Nos. 96 to 99 (comparative methods), an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp there can be attained. Further, when Al³⁺ ion concentration of the slurry in flotation is 40 ppm or less, it can be expected to obtain qualities superior thereto.

Example I-10

Waste papers (news papers/leaflets=75/25) recovered in a city were treated according to the following deinking methods, and the performances of the pulp sheet thus obtained were evaluated in the same manner as that in Example I-1. The results thereof are shown in Table I-16.

In this Example, the Ca²⁺ ion concentration of the warm water had been adjusted with CaCl₂, while the Al³⁺ ion concentration thereof had been adjusted with white water resulting from paper-making.

(1) Test Nos. 108 and 109

To a given amount of waste papers, 1% by weight (based on the waste papers) of caustic soda, 3% by weight (based on the waste papers) of sodium silicate, 3% by weight (based on the waste papers) of 30% by weight aqueous solution of hydrogen peroxide, 0.3% by weight (based on the waste papers) of an EO₁₀/PO₁₀ adduct of an amine represented by the following formula (1) as a deinking agent and warm water were added to prepare a mixture:

(C₄H₉)₃C—NH—(EO)₁₀(PO)₁₀H  (1).

The waste papers in the mixture were disintegrated at 40° C. for 10 minutes to prepare a pulp slurry having a pulp concentration of 5% by weight. The resulting pulp slurry was maintained at 40° C. for 60 minutes, and then warm water, of which Al³⁺ ion concentration and Ca²⁺ ion concentration had been suitably adjusted, was added to the pulp slurry to give a pulp slurry having a pulp concentration of 1% by weight, an Al³⁺ ion concentration given in Table I-16 and a Ca²⁺ ion concentration given in Table I-16. Hydrochloric acid was added to the pulp slurry to adjust the pH thereof to a value shown in Table I-16. After sampling from the resulting pulp slurry (before flotation), the pulp slurry was subjected to flotation at 40° C. for 10 minutes to prepare a pulp slurry (after flotation). The pulp slurries were subjected to paper-making in the same manner as that in Example I-1.

(2) Test Nos. 110 and 111

To a given amount of waste papers, 1% by weight (based on the waste papers) of caustic soda, 3% by weight (based on the waste papers) of sodium silicate, 3% by weight (based on the waste papers) of 30% by weight aqueous solution of hydrogen peroxide, 0.2% by weight (based on the waste papers) of an EO₁₀/PO₁₀ block adduct of stearyl alcohol as a deinking agent and warm water were added to prepare a mixture. The waste papers in the mixture were disintegrated at 40° C. for 10 minutes to prepare a pulp slurry having a pulp concentration of 5% by weight. The resulting pulp slurry was maintained at 40° C. for 60 minutes, and then warm water, of which Al³⁺ ion concentration and Ca²⁺ ion concentration had been suitably adjusted, was added to the pulp slurry to give a pulp slurry having a pulp concentration of 1% by weight, an Al³⁺ ion concentration given in Table I-16 and a Ca²⁺ ion concentration given in Table I-16. In Test No. 110, aluminum sulfate was also added to the pulp slurry to adjust the Al³⁺ concentration of the slurry to a value shown in Table I-16. Then, hydrochloric acid was added to the resulting pulp slurry to adjust the pH thereof to a value shown in Table I-16. Further, 0.05% by weight (based on the waste papers) of a nonionic polyacrylamide (NP 800, manufactured by Diafloc Co. Ltd.) was added to the pulp slurry. By the addition of the nonionic polyacrylamide, the pH of the resulting pulp slurry was scarcely altered. After sampling from the resulting pulp slurry (before flotation), the pulp slurry was subjected to flotation at 40° C. for 10 minutes to prepare a pulp slurry (after flotation). The pulp slurries were subjected to paper-making in the same manner as that in Example I-1.

(3) Test Nos. 112 to 114

To a given amount of waste papers, 1% by weight (based on the waste papers) of caustic soda, 3% by weight (based on the waste papers) of sodium silicate, 3% by weight (based on the waste papers) of 30% by weight aqueous solution of hydrogen peroxide, 0.2% by weight (based on the waste papers) of an EO₁₀/PO₁₀ block adduct of stearyl alcohol as a deinking agent and warm water were added to prepare a mixture. The waste papers in the mixture were disintegrated at 40° C. for 10 minutes to prepare a pulp slurry having a pulp concentration of 5% by weight. The resulting pulp slurry was maintained at 40° C. for 60 minutes, and then warm water, of which Al³⁺ ion concentration and Ca²⁺ ion concentration had been suitably adjusted, was added to the pulp slurry to give a pulp slurry having a pulp concentration of 1% by weight, an Al³⁺ ion concentration given in Table I-16 and a Ca²⁺ ion concentration given in Table I-16. Hydrochloric acid was added to the resulting pulp slurry to adjust the pH thereof to a value shown in Table I-16. Further, 0.06% by weight (based on the waste papers) of a cationic compound shown in Table I-1 or I-2, and Table I-16 was added to the pulp slurry. By the addition of the cationic compound, the pH of the resulting pulp slurry was scarcely altered. After sampling from the resulting pulp slurry (before flotation), the pulp slurry was subjected to flotation at 40° C. for 10 minutes to prepare a pulp slurry (after flotation). The pulp slurries were subjected to paper-making in the same manner as that in Example I-1.

TABLE I-16 Nonionic or cationic Residual compound Al³⁺ Ca²⁺ ink area Name or pH in ion ion Whiteness (%) ratio (%) Recovery Test number of flota- conc. conc. Before After After of pulp No. compound tion (ppm) (ppm) flotation flotation flotation (%) 108 None 4.5 30 5 42.2 52.9 0.683 87.8 109 None 7.0 15 200 42.1 52.8 0.690 87.1 110 NP-800 4.5 60 5 44.4 53.6 0.409 77.6 111 NP-800 7.0 15 200 44.6 53.4 0.418 78.2 112 a₁-3 7.0 15 200 45.3 57.7 0.118 91.1 113 b₁-1 7.0 15 200 45.2 57.7 0.126 91.6 114 b₁-11 7.0 15 200 45.3 58.1 0.114 91.5 Note) The Al³⁺ ion concentrations and the Ca²⁺ concentrations in the above Table were determined in flotation.

It is observed in Test Nos. 108 and 109 (comparative examples) that a lot of non-liberated ink spots which have not been removed from pulp by flotation is present in the reclaimed paper since the deinking agent having a poor power for liberating ink is used in the disintegrating step of waste papers. Accordingly, the reclaimed pulp is poor in quality. In Test Nos. 110 and 111 (comparative examples), the addition of the polyacrylamide optionally with aluminum sulfate causes the re-adhesion of ink to cellulose fibers, and reduces the quality of the reclaimed pulp. Further, it is observed that foaming in flotation is extremely enhanced to deteriorate the recovery of pulp.

In contrast, according to the methods of Test Nos. 112 to 114 (the methods of the present invention) wherein the flotation is effected in the presence of a cationic compound at a specific pH at a specific Ca²⁺ ion concentration and at a specific Al³⁺ ion concentration, an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp are observed.

Example I-11

Deinking test was carried out according to the method described in Example I-1 by using cationic compound i₁-1 represented by the following formula:

The result are shown in Table I-17.

TABLE I-17 Residual Cationic polymer ink area Content of weight- ratio cationic average Amount pH in Whiteness (%) (%) Recovery Test Compd. nitrogen* molecular added flota- Before After After of pulp No. No. (%) weight (%) tion flotation flotation flotation (%) 115 None — — — 10.0 45.0 52.2 0.752 86.8 116 None — — — 9.0 45.4 52.8 0.683 87.2 117 None — — — 8.0 44.9 53.3 0.411 88.3 118 None — — — 7.0 45.6 53.6 0.365 88.9 119 None — — — 6.0 45.0 54.0 0.329 88.9 120 None — — — 5.0 44.6 53.1 0.431 89.1 121 None — — — 4.0 44.3 52.9 0.625 87.6 122 i₁-1 1.50 800,000 0.01 9.0 45.2 55.8 0.260 88.7 123 i₁-1 1.50 800,000 0.01 8.0 44.6 57.5 0.149 90.5 124 i₁-1 1.50 800,000 0.01 7.0 44.7 57.8 0.142 92.7 125 i₁-1 1.50 800,000 0.01 6.0 44.6 57.2 0.153 92.4 126 i₁-1 1.50 800,000 0.0l 5.0 44.4 56.5 0.214 92.1 127 i₁-1 1.50 800,000 0.01 4.0 44.4 56.3 0.221 91.0 Note) *: The content (%) of cationic nitrogen was calculated by multiplying the nitrogen content (%) determined by Kjeldahl method by the ratio of the cationic nitrogen to the total nitrogen which was determined from the molecular formula of the polymer.

In the Tests described above, Test No. 115 is effected in a similar manner as that of a conventional industrial deinking method. According to the methods of Test Nos. 122 to 127 (the methods of the present invention) wherein the flotation is effected in the presence of a cationic compound at a specific pH, as compared with those of Test Nos. 115 to 121 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

<Amines and Acid Salts Thereof>

The amines and acid salts thereof used in the following Examples II-1 to II-10 will be shown in the following Tables II-1 to II-8.

In Tables II-1 to II-8, each numeral in the columns of R₁ to R₃ and W₁ to W₄ means the carbon atom number of a linear alkyl group as a substituent; and “18 F1”, “18 Hyd” and “12 Hyd” refer oleyl group, β-hydroxystearyl group and β-hydroxylauryl group, respectively.

TABLE II-1 General Compound Substituent formula No. R₁ R₂ R₃

a₂-1 a₂-2 a₂-3 a₂-4 a₂-5 a₂-6 a₂-7 a₂-8 a₂-9 a₂-10 a₂-11 a₂-12 a₂-13 a₂-14 12 12 12 12 # 18 18 18 18 18 18 F1 18 Hyd 22 22 22 H 1 8 12 H 1 2 4 18 18 F1 1 1 8 22 #H 1 1 12 H H 2 4 1 1 1 H 1 1

TABLE II-2 General Compound Substituent and acid portion formula No. R₁ R₂ R₃ HA

b₂-1 b₂-2 b₂-3 b₂-4 b₂-5 b₂-6 b₂-7 b₂-8 b₂-9 b₂-10 b₂-11 b₂-12 b₂-13 b₂-14 #12 12 12 12 18 18 18 18 18 18 F1 18 Hyd 22 22 22 H 1 8 12 H 1 2 4 18 #18 F1 1 1 8 22 H 1 1 12 H H 2 4 1 1 1 H 1 1 CH₃COOH HCl HCl HNO₃ #H₂SO₄* CH₃COOH H₂SO₄* HCl HCl HCl HCl HCl HCl HCl Note) The sulfuric acid was used in an amount of ½ mole per mole of amine.

TABLE II-3 Substituent and symbol General Compound AO formula No. R₁ 1 + m EO/PO

c₂-1 c₂-2 c₂-3 c₂-4 c₂-5 12 22 18 18 22  4  10 100 300 100 100/0  0/100  50/50 100/0  70/30 Note) Ethylene oxide and propylene oxide were added at random.

TABLE II-4 Substituent and Compound acid portion General formula No. R₁ HA R₁CONHCH₂CH₂NH₂ · HA d₂-1 12 HCl d₂-2 18 CH₃COOH d₂-3 22 H₂SO₄* d₂-4 18 F1 HCl d₂-5 18 Hyd HCl Note) The sulfuric acid was used in an amount of 1/2 mole per mole of amine.

TABLE II-5 Substituent and Compound acid portion General formula No. R₁ HA

e₂-1 e₂-2 e₂-3 12 18 22 HCl HCl HCl

TABLE II-6 Substituent and Compound acid portion General formula No. R₁ HA

f₂-1 f₂-2 f₂-3 12 18 22 HCl HCl HCl

TABLE II-7 Compound Substituent General formula No. W₁ W₂ W₃ W₄

g₂-1 g₂-2 g₂-3 g₂-4 g₂-5 g₂-6 18 H 1 H 1 H H 18 H H 12 22 H #H 12 H 1 H H H 1 22 18 2

TABLE II-8 Substituent General formula Compound No. W₁ W₂ W₃

h₂-1 h₂-2 h₂-3 12 H H H 18  1 H  2 22

Example II-1

Deinking test was carried out in a similar manner as that in Example I-1 except that the pH of the pulp slurries were each adjusted to a value shown in Table II-9 and that amines and acid salts of amines shown in Tables II-1 and II-2, and Table II-9 were used instead of the cationic compounds. By the addition of the amine or the acid salt of an amine, the pH of the slurry was scarcely altered (the same will be applied to the following Examples II-2 to II-10).

The results thereof are shown in Table II-9.

TABLE II-9 Residual Reco- Amine or acid salt ink area very of amine pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%)  1 None — 10.0 45.0 52.2 0.752 86.8  2 None — 9.0 45.4 52.8 0.683 87.2  3 None — 8.0 44.9 53.3 0.414 88.3  4 None — 7.0 45.5 53.6 0.365 88.9  5 None — 6.0 45.0 54.0 0.329 88.9  6 None — 5.0 44.6 53.1 0.431 89.1  7 None — 4.0 44.3 52.9 0.625 87.6  8 a₂-1 0.10 9.0 45.7 56.0 0.240 89.0  9 a₂-1 0.10 8.0 45.3 56.9 O:149 88.7 10 a₂-1 0.10 7.0 45.3 57.7 0.144 92.9 11 a₂-1 0.10 6.0 45.2 57.3 0.166 92.2 12 a₂-1 0.10 5.0 45.0 57.0 0.210 92.5 13 a₂-1 0.10 4.0 44.5 56.3 0.227 91.2 14 a₂-2 0.06 9.0 45.3 55.9 0.247 89.3 15 a₂-2 0.06 8.0 45.0 57.7 0.156 88.9 16 a₂-2 0.06 7.a 44.g 57.6 0.147 93.2 17 a₂-2 0.06 6.0 44.9 57.1 0.173 92.4 18 a₂-2 0.06 5.0 44.6 56.8 0.215 92.8 19 a₂-2 0.06 4.0 44.5 56.1 0.233 91.4 20 b₂-6 0.03 9.0 45.2 55.6 0.244 87.7 21 b₂-6 0.03 8.0 45.0 57.7 0.154 87.3 22 b₂-6 0.03 7.0 44.8 57.3 0.149 91.4 23 b₂-6 0.03 6.0 44.9 57.1 0.170 90.8 24 b₂-6 0.03 5.0 44.5 56.6 0.214 91.3 25 b₂-6 0.03 4.0 44.2 56.1 0.230 90.0 Note) The amount of the amine or acid salt thereof is expressed by % by weight based on the waste papers (i.e., the absoluted dry weight of the waste papers). The same will be applied to the following Examples II-2 to II-10.

In the tests described above, Test No. 1 is effected in a similar manner as that of a conventional industrial deinking method. According to the methods of Test Nos. 8 to 25 (the methods of the present invention) wherein the flotation is effected in the presence of an amine or an acid salt of an amine at a specific pH, as compared with those of Test Nos. 1 to 7 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

Example II-2

Deinking test was carried out according to the method described in Example II-1 by using amines shown in Tables II-1 and II-10. The results are shown in Table II-10.

TABLE II-10 Residual Reco- ink area very Amine pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 26 None — 10.0 45.1 52.0 0.754 86.9 27 None — 7.0 45.3 54.4 0.442 88.9 28 a₂-1 0.10 7.0 45.3 57.9 0.139 92.1 29 a₂-2 0.10 7.0 45.2 57.7 0.145 92.7 30 a₂-3 0.10 7.0 45.0 57.5 0.143 92.7 31 a₂-4 0.10 7.0 45.0 56.9 0.151 93.3 32 a₂-5 0.10 7.0 45.5 57.8 0.142 92.7 33 a₂-6 0.10 7.0 45.6 57.8 0.141 92.4 34 a₂-7 0.10 7.0 45.4 57.8 0.136 92.4 35 a₂-8 0.10 7.0 45.5 57.6 0.142 92.7 36 a₂-9 0.10 7.0 45.0 57.5 0.145 92.1 37 a₂-10 0.10 7.0 45.1 57.5 0.155 93.5 38 a₂-11 0.10 7.0 45.1 57.3 0.145 93.0 39 a₂-12 0.10 7.0 45.3 57.2 0.146 92.6 40 a₂-13 0.10 7.0 45.1 57.1 0.148 92.6 41 a₂-14 0.10 7.0 44.8 56.8 0.162 93.8 42 a₂-1/ 0.05/0.05 7.0 45.3 57.7 0.144 92.7 a₂-5

According to the methods of Test Nos. 28 to 42 (the methods of the present invention) wherein the flotation is effected in the presence of an amine shown in Table II-1 at a specific pH, as compared with those of Test Nos. 26 and 27 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

Example II-3

Deinking test was carried out according to the method described in Example II-1 by using acid salts of amines shown in Tables II-2 and II-11, optionally together with amine a₂-10 shown in Table II-1. The results are shown in Table II-11.

TABLE II-11 Residual reco- Amine and acid salt ink area very of amine pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 43 None — 10.0 45.1 52.1 0.749 86.8 44 None — 1.0 4s.3 54.2 0.449 88.7 45 b₂-1 0.05 7.0 45.3 57.2 0.184 92.0 46 b₂-1 0.10 7.0 45.2 57.9 0.145 92.7 47 b₂-1 0.20 7.0 45.0 58.9 0.101 93.5 48 b₂-2 0.10 7.0 45.1 57.5 0.144 92.B 49 b₂-3 0.10 7.0 44.9 57.7 0.142 92.6 50 b₂-4 0.10 7.0 45.1 56.7 0.1 57 93.4 51 b₂-5 0.10 7.0 45.4 58.0 0.132 92.6 52 b₂-6 0.10 7.0 45.5 57.6 0.138 92.3 53 b₂-7 0.10 7.0 45.3 58.0 0.135 92.2 54 b₂-8 0.10 7.0 45.4 57.4 0.143 92.8 55 b₂-9 0.10 7.0 45.1 57.7 0.138 92.6 56 b₂-10 0.10 7.0 45.0 57.3 0.145 93.3 57 b₂-11 0.10 0 45.2 57.5 0.139 92.9 58 b₂-12 0.10 7.0 45.2 57.0 0.148 92.8 59 b₂-13 0.10 7.0 45.2 56.9 0.151 92.7 60 b₂-14 0.10 7.0 44.7 58.6 0.184 93.9 61 b₂-2/ 0.05/0.05 7.0 45.4 57.7 0.139 92.5 a₂-10

According to the methods of Test Nos. 45 to 61 (the methods of the present invention) wherein the flotation is effected in the presence of an acid salt of an amine shown in Table II-2 optionally together with amine a₂-10 shown in Table II-1 at a specific pH, as compared with those of Test Nos. 43 and 44 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

Example II-4

Deinking test was carried out according to the method described in Example II-1 by using amines shown in Tables II-3 and II-12. An EO₂₀ adduct of stearic acid was used as the deinking agent in the present Example. The results are shown in Table II-12.

TABLE II-12 Residual Reco- ink area very Amine pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 62 None — 10.0 45.2 52.1 0.769 86.9 63 None — 7.0 45.5 54.1 0.462 88.1 64 c₂-1 0.05 7.0 45.4 57.8 0.138 92.8 65 c₂-2 0.05 7.0 44.7 56.6 0.193 93.9 66 c₂-3 0.05 7.0 45.0 58.0 0.140 92.2 67 c₂-4 0.05 7.0 45.6 58.1 0.134 92.9 68 c₂-5 0.05 7.0 45.6 58.0 0.138 92.2

According to the methods of Test Nos. 64 to 68 (the methods of the present invention) wherein the flotation is effected in the presence of an amine shown in Table II-3 at a specific pH, as compared with those of Test Nos. 62 and 63 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

Example II-5

Deinking test was carried out according to the method described in Example II-1 by using acid salts of amines shown in Tables II-4 to II-6, and Table II-13. An EO₆₀ adduct of a mixture (1:1 by mole) of beef tallow and glycerol was used as the deinking agent in the present Example. The results are shown in Table II-13.

TABLE II-13 Residual Reco- Acid salt of ink area very amine pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 69 None — 10.0 45.0 53.1 0.709 85.9 70 None — 7.#O 45.4 54.6 0.411 86.1 71 d₂-1 0.10 7.0 44.9 57.4 0.139 91.7 72 d₂-2 0.10 7.0 45.3 57.6 0.139 92.9 73 d₂-3 0.10 7.0 45.2 56.9 0.146 92.2 74 d₂-4 0.10 7.0 45.0 56.7 a.156 93.5 75 d₂-5 0.10 7.0 45.1 57.0 0.147 91.7 76 e₂-1 0.10 7.0 45.1 57.4 0.140 92.2 77 e₂-2 0.10 7.0 45.2 57.6 0.144 92.7 78 e₂-3 0.10 7.0 45.4 57.2 0.153 93.3 79 f₂-1 0.10 7.0 44.8 57.3 0.148 92.4 80 f₂-2 0.10 7.0 45.2 57.4 0.145 92.8 81 f₂-3 0.10 7.0 45.5 56.7 0.159 93.3

According to the methods of Test Nos. 71 to 81 (the methods of the present invention) wherein the flotation is effected in the presence of an acid salt of an amine shown in Table II-4, II-5 or II-6 at a specific pH, as compared with those of Test Nos. 69 and 70 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

Example II-6

Deinking test was carried out according to the method described in Example II-1 by using amines shown in Tables II-7 and II-8, and Table II-14. The results are shown in Table II-14.

TABLE II-14 Residual Reco- ink area very Amine pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 82 None — 10.0 45.0 52.0 0.752 86.6 83 None — 7.0 45.4 54.3 0.444 88.4 84 g₂-1 0.10 7.0 45.2 58.0 0.134 92.2 85 g₂-2 0.10 7.0 45.2 58.2 0.130 92.1 86 g₂-3 0 10 7.0 45.1 58.1 0.131 92.0 87 g₂-4 0.10 7.0 44.9 57.9 0.141 92.8 88 g₂-5 0.10 7.0 45.3 57.8 0.142 92.5 89 g₂-6 0.10 7.0 44.9 57.7 0.145 92.1 90 h₂-1 0.10 7.0 45.4 58.2 0.131 92.1 91 h₂-2 0.10 7.0 45.2 57.9 0.142 92.4 92 h₂-3 0.10 7.0 45.0 57.5 0.144 92.8

According to the methods of Test Nos. 84 to 92 (the methods of the present invention) wherein the flotation is effected in the presence of an amine shown in Table II-7 or II-8 at a specific pH, as compared with those of Test Nos. 82 and 83 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

Example II-7

Deinking test was carried out in a similar manner as that In Example I-7 except that the pH of the pulp slurries were each adjusted to a value shown in Table II-15 and that amines and acid salts of amines shown in Tables II-1, II-2 and II-3, and Table II-15 were used instead of the cationic compounds. The results thereof are shown in Table II-15.

TABLE II-15 Amine and acid Residual Reco- Deinking salt of amine ink area very agent No. Amount pH in Whiteness (%) ratio (%) of Test (See Table Compd. added flota- Before After After pulp No. I-12 No. (%) tion flotation flotation flotation (%) 93 A1 None — 10.0 43.9 51.0 0.841 88.5 94 A2 None — 10.0 44.0 52.2 0.785 86.5 95 A3 None — 10.0 44.6 52.1 0.771 86.2 96 A4 None — 10.0 47.8 53.5 0.415 90.0 97 A1 a₂-l 0.10 7.0 44.4 56.5 0.196 92.4 98 A2 a₂-2 0.10 7.0 44.6 57.8 0.149 91.1 99 A3 b₂-6 0.10 7.0 44.8 57.4 0.157 90.4 100  A4 c₂-1 0.05 7.0 47.3 58.9 0.142 94.2

According to the methods of Test Nos. 97 to 100 (the methods of the present invention) wherein various deinking agents are each used and the flotation is effected in the presence of an amine or an acid salt of an amine at a specific pH, as compared with those of Test Nos. 93 to 96 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp.

Example II-8

Deinking test was carried out in a similar manner as that in Example I-8 except that the Ca²⁺ ion concentrations and the pH of the pulp slurries were each adjusted to a value shown in Table II-16 and that amines and acid salts of amines shown in Tables II-1 and II-2, and Table II-16 were used instead of the cationic compounds.

The results thereof are shown in Table II-16.

TABLE II-16 Amine and acid Residual Reco- salt of amine Ca²⁺ ion ink area very Amount pH in concent- Whiteness (%) ratio (%) of Test Compound added flota- ration Before After After pulp No. No. (%) tion (ppm) flotation flotation flotation (%) 101 None — 10.0 0 44.8 52.1 0.770 86.4 102 None — 10.0 50 45.0 52.2 0.752 86.8 103 None — 10.0 100 45.3 52.5 0.743 87.3 104 None — 10.0 200 45.2 52.6 0.739 87.3 105 None — 10.0 400 45.0 52.3 0.765 87.6 106 None — 10.0 800 44.7 51.8 0.781 87.6 107 a₂-1 0.10 7.0 0 45.3 57.7 0.144 92.9 108 a₂-1 0.10 7.0 50 45.5 58.0 0.126 92.3 109 a₂-1 0.10 7.0 100 45.8 58.8 0.071 92.1 110 a₂-1 0.10 7.0 200 45.9 59.6 0.065 92.3 111 a₂-1 0.10 7.0 400 45.6 58.1 0.106 93.2 112 a₂-1 0.10 7.0 800 45.4 57.2 0.178 94.1 113 a₂-2 0.06 7.0 0 44.9 57.6 0.147 93.2 114 a₂-2 0.06 7.0 200 45.4 59.5 0.066 92.6 115 a₂-2 0.06 7.0 800 44.9 57.2 0.181 93.8 116 b₂-6 0.03 7.0 0 44.8 57.3 0.149 91.4 117 b₂-6 0.03 7.0 200 45.2 59.1 0.075 90.8 118 b₂-6 0.03 7.0 800 44.8 56.8 0.189 92.6 Note) The Ca²⁺ ion concentrations in the above Table were determined in flotation.

According to the methods of Test Nos. 107 to 118 (the methods of the present invention) wherein the flotation is effected in the presence of an amine or an acid salt of an amine at a specific pH at a specific Ca²⁺ ion concentration, as compared with those of Test Nos. 101 to 106 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

Example II-9

Deinking test was carried out in a similar manner as that in Example I-9 except that the Al³⁺ ion concentrations, the Ca²⁺ ion concentrations and the pH of the pulp slurries were each adjusted to a value shown in Table II-17 and that amines and acid salts of amines shown in Tables II-1 and II-2, and Table II-17 were used instead of the cationic compounds. For the adjustment of the Ca²⁺ ion concentration, CaCl₂ was used, and for the adjustment of Al³⁺ ion concentration, white water resulting from paper-making, or the white water and aluminum sulfate (in Test Nos. 122, 126 and 130) was(were) used. Further, for the adjustment of pH, hydrochloric acid or sodium hydroxide was used.

The results thereof are shown in Table II-17.

TABLE II-17 Residual Amine and acid ink area Reco- salt of amine Al³⁺ Ca²⁺ Whiteness (%) ratio (%) very Amount pH in ion ion Before After After of Test Compd. added flota- conc. conc. flota- flota- flota- pulp No. No. (%) tion (ppm) (ppm) tion tion tion (%) 119 None — 10.0 0 100 45.3 52.5 0.743 87.3 120 None — 10.0 20 100 45.5 52.2 0.776 85.2 121 None — 10.0 40 100 44.4 51.9 0.802 82.7 122 None — 10.0 60 100 43.4 51.7 0.822 79.3 123 a₂-1 0.10 7.0 0 100 45.8 58.8 0.071 92.1 124 a₂-1 0.10 7.0 20 100 45.9 58.0 0.106 90.2 125 a₂-1 0.10 7.0 40 100 45.2 56.7 0.212 87.7 126 a₂-1 0.10 7.0 60 100 44.1 54.0 0.387 84.3 127 a₂-2 0.06 7.0 20 100 45.4 57.7 0.107 90.6 128 a₂-2 0.06 7.0 60 100 43.9 53.8 0.489 84.5 129 b₂-6 0.03 7.0 20 100 45.1 57.3 0.116 88.6 130 b₂-6 0.03 7.0 60 100 43.5 53.6 n.505 82.9 Note) The Al³⁺ ion concentrations and the Ca²⁺ ion concentrations in the above Table were determined in flotation.

According to the methods of Test Nos. 123 to 130 (the methods of the present invention) wherein the flotation is effected in the presence of an amine or an acid salt of an amine at a specific pH at a specific Ca²⁺ ion concentration, as compared with those of Test Nos. 119 to 122 (comparative methods), an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp there can be attained. Further, when Al³⁺ ion concentration of the slurry in flotation is 40 ppm or less, it can be expected to obtain qualities superior thereto.

Example II-10

Waste papers (news papers/leaflets=75/25) recovered in a city were treated according to the following deinking methods, and the performances of the pulp sheet thus obtained were evaluated in the same manner as that in Example I-1. The results thereof are shown in Table II-18.

In this Example, the Ca²⁺ ion concentration of the warm water had been adjusted with CaCl₂, while the Al³⁺ ion concentration thereof had been adjusted with white water resulting from paper-making.

(1) Test Nos. 131 and 132

The pulp sheet were prepared in a similar manner as that in Example I-10-(1) except that the Al³⁺ ion concentrations, the Ca²⁺ ion concentrations and the pH of the pulp slurries were each adjusted to a value shown in Table II-18.

(2) Test Nos. 133 and 134

The pulp sheet were prepared in a similar manner as that in Example I-10-(2) except that the Al³⁺ ion concentrations, the Ca²⁺ ion concentrations and the pH of the pulp slurries were each adjusted to a value shown in Table II-18. In Test No. 133, aluminum sulfate was also added to the pulp slurry to adjust the Al³⁺ concentration of the slurry to a value shown in Table II-18.

(3) Test Nos. 135 and 136

The pulp sheet were prepared in a similar manner as that in Example I-10-(3) except that the Al³⁺ ion concentrations, the Ca²⁺ ion concentrations and the pH of the pulp slurries were each adjusted to a value shown in Table II-18 and that 0.1% by weight (based on the waste papers) of amine a₂-1 shown in Table II-1 or acid salt of amine b₂-5 shown in Table II-2 was used instead of the cationic compound.

TABLE II-18 Nonionic compound, Residual Reco- amine or acid Al³⁺ Ca²⁺ ink area very salt of amine pH in ion ion Whiteness (%) ratio (%) of Test Name or number flota- conc. conc. Before After After pulp No. of compound tion (ppm) (ppm) flotation flotation flotation (%) 131 None 4.5 30 5 42.2 52.9 0.683 87.8 132 None 7.0 15 200 42.1 52.8 0.690 87.1 133 NP-800 4.5 60 5 44.4 53.6 0.409 77.6 134 NP-800 7.0 15 200 44.6 53.4 0.418 78.2 135 a₂-1 7.0 15 200 45.5 58.8 0.106 91.3 136 b₂-5 7.0 15 200 45.4 58.9 0.112 91.6 Note) The Al³⁺ ion concentrations and the Ca²⁺ ion concentrations in the above Table were determined in flotation.

It is observed in Test Nos. 131 and 132 (comparative examples) that a lot of non-liberated ink spots which have not been removed from pulp by flotation is present in the reclaimed paper since the deinking agent having a poor power for liberating ink is used in the disintegrating step of waste papers. Accordingly, the reclaimed pulp is poor in quality. In Test Nos. 133 and 134 (comparative examples), the addition of the polyacrylamide optionally with aluminum sulfate causes the re-adhesion of ink to cellulose fibers, and reduces the quality of the reclaimed pulp. Further, it is observed that foaming in flotation is extremely enhanced to deteriorate the recovery of pulp.

In contrast, according to the methods of Test Nos. 134 and 135 (the methods of the present invention) wherein the flotation Is effected in the presence of an amine or an acid salt of an amine at a specific pH at a specific Ca²⁺ ion concentration and at a specific Al³⁺ ion concentration, an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp are observed.

Example II-11

Deinking test was carried out according to the method described in Example II-1 by using an acid salt of an amine represented by the following formula:

The results are shown in Table II-19.

TABLE II-19 Residual ink area Polymer ratio Content of weight- Whiteness (%) (%) Reco- derived average Amount pH in Before After After very of Test Compd. from amino molecular added flota- flota- flota- flota- pulp No. No. groups* (%) weight (%) tion tion tion tion (%) 137 None — — — 10.0 45.0 52.2 0.752 86.8 138 None — — — 9.0 45.4 52.8 0.683 87.2 139 None — — — 8.0 44.9 53.3 0.411 88.3 140 None — — — 7.0 45.6 53.6 0.365 88.9 141 None — — — 6.0 45.0 54.0 0.329 88.9 142 None — — — 5.0 44.6 53.1 0.431 89.1 143 None — — — 4.0 44.3 52.9 0.625 87.6 144 l₂-1 6.40 300,000 0.01 9.0 45.3 54.6 0.302 88.9 145 l₂-1 6.40 300,000 0.01 8.0 44.8 56.8 0.178 90.7 146 l₂-1 6.40 300,000 0.01 7.0 45.0 57.0 0.165 92.8 147 l₂-1 6.40 300,000 0.01 6.0 44.9 56.7 0.192 92.0 148 l₂-1 6.40 300,000 0.01 5.0 44.7 56.1 0.248 91.5 149 l₂-1 6.40 300,000 0.01 4.0 44.6 55.8 0.286 90.3 Note) *: The content (%) of nitrogen derived from amino groups was calculated by multiplying the nitrogen content (%) determined by Kjeldahl method by the ratio of the nitrogen derived from amino groups to the total nitrogen which was determined from the molecular formula of the polymer.

In the tests described above, Test No. 137 is effected in a similar manner as that of a conventional industrial deinking method. According to the methods of Test Nos. 144 to 149 (the methods of the present invention) wherein the flotation is effected in the presence of an amine or an acid salt of an amine at a specific pH, as compared with those of Test Nos. 137 to 143 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

<Amphoteric Compounds>

The amphoteric compounds used in the following Examples III-1 to III-16 will be shown in the following Tables III-1 to III-12.

In Tables III-1 to III-12, each numeral in the columns of R₁ to R₄ means the carbon atom number of a linear alkyl group as a substituent; and “18 F1”, “18 Hyd” and “12 Hyd” refer oleyl group, β-hydroxystearyl group and β-hydroxylauryl group, respectively.

TABLE III-1 General Compound Substituent formula No. R₁ R₂ R₃

a₃-1 a₃-2 a₃-3 a₃-4 a₃-5 12 18 18 18 F1 22 1 18 2 8 12 1 1 2 1 12

TABLE III-2 General Compound Substituent formula No. R₁ R₂ R₃

b₃-1 b₃-2 b₃-3 b₃-4 b₃5 12 18 18 18 F1 22 1 18 2 8 12 1 1 2 1 12

TABLE III-3 General Compound Substituent formula No. R₅ in Y₁ R₅ in Y₂ M

c₃-1 c₃-2 c₃-3 12 18 18 F1 18 H 1 H Na NH₄

TABLE III-4 Compound Substituent General formula No. R₄ M

d₃-1 d₃-2 d₃-3 d₃-4 d₃-5 12 18 22 18 F1 18 Hyd Na Na NH₄ Na Na

TABLE III-5 Compound Substituent General formula No. R₄ M

e₃-1 e₃-2 e₃-3 e₃-4 e₃-5 12 18 22 18 F1 18 Hyd Na Na NH₄ Na Na

TABLE III-6 General Compound Substituent formula No. R₄ Z₁ Z₂

f₃-1 f₃-2 f₃-4 f₃-5 12 18 22 18 F1 18 Hyd CH₂COONa CH₂COOH CH₂COOH CH₂COOH CH₂COOH #CH₂COONa H CH₂COOH H H

TABLE III-7 Compound Substituent General formula No. R₄ M R₄NHCH₂CH₂COOM g₃-1 12 Na g₃-2 18 Na g₃-3 22 NH₄ g₃-4 18 F1 Na g₃-5 18 Hyd Na

TABLE III-8 Compound Substituent General formula No. R₄ M R₄NH(CH₂)₅COOM h₃-1 12 Na h₃-2 18 Na h₃-3 22 NH₄ h₃-4 18 FI Na h₃-5 18 Hyd Na

TABLE III-9 General Compound Substituent formula No. R₁ R₂ R₃

i₃-1 i₃-2 i₃-3 i₃-4 i₃-5 12 18 18 18 Fl 22 1 18  2 8 12  1 1 2 1 12 

TABLE III-10 Compound Substituent General formula No. R₄

j₃-1 j₃-2 j₃-3 j₃-4 j₃-5 12 18 22 18 Fl 18 Hyd

TABLE III-11 Compound No. Kind of compound Phospholipid k₃-1 Soybean lecithin k₃-2 Phosphatidyl choline derived from egg k₃-3 Phosphatidyl ethanolamine derived from soybean

TABLE III-12 Compound No. Kind of compound Protein l₃-1 Soybean protein l₃-2 Casein l₃-3 Lactalbumin

Example III-1

Deinking test was carried out in a similar manner as that in Example I-1 except that the pH of the pulp slurries were each adjusted to a value shown in Table III-13 and that amphoteric compounds shown in Tables III-1, III-2 and III-3, and Table III-13 were used instead of the cationic compounds. By the addition of the amphoteric compound, the pH of the slurry was scarcely altered (the same will be applied to the following Examples III-2 to III-16).

The results thereof are shown in Table III-13.

TABLE III-13 Residual Reco- Amphoteric ink area very compound pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%)  1 None — 10.0 45.0 52.2 0.752 86.8  2 None — 9.0 45.4 52.8 0.683 87.2  3 None — 8.0 44.9 53.3 0.411 88.3  4 None — 7.0 45.6 53.6 0.365 88.9  5 None — 6.0 45.0 54.0 0.329 88.9  6 None — 5.0 44.6 53.1 0.431 89.1  7 None — 4.0 44.3 52.9 0.625 87.6  8 a₃-1 0.06 9.0 45.0 56.2 0.258 89.0  9 a₃-1 0.06 8.0 44.9 57.9 0.157 89.0 10 a₃-1 0.06 7.0 44.9 57.7 0.155 93.0 11 a₃-1 0.06 6.0 44.9 57.3 0.186 92.3 12 a₃-1 0.06 5.0 44.9 57.1 0.226 92.7 13 a₃-1 0.06 4.0 44.8 56.5 0.246 91.2 14 b₃-1 0.06 9.0 45.0 56.3 0.253 88.9 15 b₃-1 0.06 8.0 45.0 57.2 0.152 88.7 16 b₃-1 0.06 7.0 44.9 56.9 0.151 92.8 17 b₃-1 0.06 6.0 44.9 56.6 0.172 92.3 18 b₃-1 0.06 5.0 44.8 56.5 0.220 92.3 19 b₃-1 0.06 4.0 44.8 56.4 0.248 91.2 20 c₃-2 0.06 9.0 45.1 55.9 0.239 87.7 21 c₃-2 0.06 8.0 45.0 57.0 0.1 50 87.2 22 c₃-2 0.06 7.0 44.9 57.2 0.144 91.3 23 c₃-2 0.06 6.0 44.9 57.4 0.141 90.7 24 c₃-2 0.06 5.0 44.7 57.3 0.150 91.1 25 c₃-2 0.06 4.0 44.5 56.7 0.216 89.7 Note) The amount of the amphoteric compound is expressed by % by weight based on the waste papers (i.e., the absoluted dry weight of the waste papers). The same will be applied to the following Examples III-2 to III-16.

In the tests described above, Test No. 1 is effected in a similar manner as that of a conventional industrial deinking method. According to the methods of Test Nos. 8 to 25 (the methods of the present invention) wherein the flotation is effected in the presence of an amphoteric compound at a specific pH, as compared with those of Test Nos. 1 to 7 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

Example III-2

Deinking test was carried out according to the method described in Example III-1 by using amphoteric compounds shown in Tables III-1 and III -14. The results are shown in Table III-14.

TABLE III-14 Residual Reco- Amphoteric ink area very compound pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 26 None — 10.0 45.2 52.1 0.769 86.8 27 None — 7.0 45.4 54.5 0.429 88.7 28 a₃-1 0.10 7.0 44.9 58.1 0.135 91.9 29 a₃-2 0.10 7.0 45.0 57.4 0.146 93.7 30 a₃-3 0.10 7.0 45.2 57.6 0.138 92.6 31 a₃-4 0.10 7.0 44.6 57.2 0.155 93.5 32 a₃-5 0.10 7.0 45.2 57.1 0.159 93.4

According to the methods of Test Nos. 28 to 32 (the methods of the present invention) wherein the flotation is effected in the presence of an amphoteric compound shown in Table III-1 at a specific pH, as compared with those of Test Nos. 26 and 27 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp.

Example III-3

Deinking test was carried out according to the method described in Example III-1 by using amphoteric compounds shown in Tables III-2 and III-15. The results are shown in Table III-15.

TABLE III-15 Residual Reco- Amphoteric ink area very compound pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 33 None — 10.0 45.1 52.3 0.757 86.6 34 None — 7.0 45.4 54.4 0.434 88.8 35 b₃-1 0.10 7.0 45.1 58.0 0.136 91.8 36 b₃-2 0.10 7.0 45.1 57.5 0.145 93.4 37 b₃-3 0.10 7.0 45.0 57.5 0.146 92.4 38 b₃-4 0.10 7.0 44.9 57.1 0.152 93.5 39 b₃-5 0.10 7.0 45.2 57.1 0.155 93.6

According to the methods of Test Nos. 35 to 39 (the methods of the present invention) wherein the flotation is effected in the presence of an amphoteric compound shown in Table III-2 at a specific pH, as compared with those of Test Nos. 33 and 34 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp.

Example III-4

Deinking test was carried out according to the method described in Example III-1 by using amphoteric compounds shown in Tables III-3 and III-16. An EO₂₀ adduct of stearic acid was used as the deinking agent in the present Example. The results are shown in Table III-16.

TABLE III-16 Residual Reco- Amphoteric ink area very compound pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 40 None — 10.0 45.1 52.1 0.767 86.6 41 None — 7.0 45.3 54.3 0.436 88.7 42 c₃-1 0.10 7.0 45.4 57.4 0.144 92.2 43 c₃-2 0.10 7.0 45.3 58.0 0.136 91.9 44 c₃-5 0.10 7.0 45.4 57.8 0.140 92.1

According to the methods of Test Nos. 42 to 44 (the methods of the present invention) wherein the flotation is effected in the presence of an amphoteric compound shown in Table III-3 at a specific pH, as compared with those of Test Nos. 40 and 41 comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp.

Example III-5

Deinking test was carried out according to the method described in Example III-1 by using amphoteric compounds shown in Table III-4 and III-₁₇. An EO₆₀ adduct of a mixture (1:1 by mole) of beef tallow and glycerol was used as the deinking agent in the present Example. The results are shown in Table III-17.

TABLE III-17 Residual Reco- Amphoteric ink area very compound pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 45 None — 10.0 45.2 52.3 0.755 86.5 46 None — 7.0 45.2 54.1 0.441 88.6 47 d₃-1 0.10 7.0 45.2 58.0 0.137 91.5 48 d₃-2 0.10 7.0 45.1 57.4 0.145 91.8 49 d₃-3 0.10 7.0 45.3 57.3 0.151 92.2 50 d₃-4 0.10 7.0 44.9 57.1 0.158 92.1 51 d₃-5 0.10 7.0 45.1 57.5 0.140 92.6

According to the methods of Test Nos. 47 to 51 (the methods of the present invention) wherein the flotation is effected in the presence of an amphoteric compound shown in Table III-4 at a specific pH, as compared with those of Test Nos. 45 and 46 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp.

Example III-6

Deinking test was carried out according to the method described in Example III-1 by using amphoteric compounds shown in Tables III-5 and III-18. The results are shown in Table III-18.

TABLE III-18 Residual Reco- Amphoteric ink area very compound pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 52 None — 10.0 45.3 52.1 0.760 86.5 53 None — 7.0 45.2 54.3 0.433 89.0 54 e₃-1 0.10 7.0 45.3 57.7 0.144 91.4 55 e₃-2 0.10 7.0 45.3 57.5 0.145 92.0 56 e₃-3 0.10 7.0 45.2 57.6 0.146 92.1 57 e₃-4 0.10 7.0 45.2 57.4 0.147 92.5 58 e₃-5 0.10 7.0 45.2 57.4 0.146 92.6

According to the methods of Test Nos. 54 to 58 (the methods of the present invention) wherein the flotation is effected in the presence of an amphoteric compound shown in Table III-5 at a specific pH, as compared with those of Test Nos. 52 and 53 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp.

Example III-7

Deinking test was carried out according to the method described in Example III-1 by using amphoteric compounds shown in Tables III -6 and III-19. The results are shown in Table III-19.

TABLE III-19 Residual Reco- Amphoteric ink area very compound pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 59 None — 10.0 45.2 52.1 0.761 86.5 60 None — 7.0 45.3 54.4 0.439 88.7 61 f₃-1 0.10 7.0 45.2 57.6 0.145 91.7 62 f₃-2 0.10 7.0 45.2 57.3 0.148 92.2 63 f₃-3 0.10 7.0 45.3 57.5 0.146 92.3 64 f₃-4 0.10 7.0 45.1 57.6 0.147 92.1 65 f₃-5 0.10 7.0 45.2 57.5 0.147 92.4

According to the methods of Test Nos. 61 to 65 (the methods of the present invention) wherein the flotation is effected in the presence of an amphoteric compound shown in Table III-6 at a specific pH, as compared with those of Test Nos. 59 and 60 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp.

Example III-8

Deinking test was carried out according to the method described in Example III-1 by using amphoteric compounds shown in Tables III-7 and III-20. The results are shown in Table III-20.

TABLE III-20 Residual Reco- Amphoteric ink area very compound pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 66 None — 10.0 45.1 52.1 0.754 86.5 67 None — 7.0 45.3 54.2 0.439 88.9 68 g₃-1 0.10 7.0 45.2 57.8 0.137 92.3 69 g₃-2 0.10 7.0 45.2 57.7 0.145 92.9 70 g₃-3 0.10 7.0 45.3 57.5 0.147 93.1 71 g₃-4 0.10 7.0 45.0 57.3 0.156 93.4 72 g₃-5 0.10 7.0 45.1 57.5 0.150 93.1

According to the methods of Test Nos. 68 to 72 (the methods of the present invention) wherein the flotation is effected in the presence of an amphoteric compound shown in Table III-7 at a specific pH, as compared with those of Test Nos. 66 and 67 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp.

Example III-9

Deinking test was carried out according to the method described in Example III-1 by using amphoteric compounds shown in Tables III-8 and III-21. The results are shown in Table III-21.

TABLE III-21 Residual Reco- Amphoteric ink area very compound pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 73 None — 10.0 45.1 52.2 0.759 86.7 74 None — 7.0 45.4 54.4 0.435 88.7 75 h₃-1 0.10 7.0 45.1 57.6 0.146 92.2 76 h₃-2 0.10 7.0 45.1 57.5 0.144 92.3 77 h₃-3 0.10 7.0 45.1 57.4 0.146 92.8 78 h₃-4 0.10 7.0 45.2 57.1 0.162 93.1 79 h₃-5 0.10 7.0 45.0 57.5 0.145 92.4

According to the methods of Test Nos. 75 to 79 (the methods of the present invention) wherein the flotation is effected in the presence of an amphoteric compound shown in Table III-8 at a specific pH, as compared with those of Test Nos. 73 and 74 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp.

Example III-10

Deinking test was carried out according to the method described in Example III-1 by using amphoteric compounds shown in Tables III-9 and III-22. The results are shown in Table III-22.

TABLE III-22 Residual Reco- Amphoteric ink area very compound pH in Whiteness (%) ratio (%) of Test Compound Amount flota- Before After After pulp No. No. added (%) tion flotation flotation flotation (%) 80 None — 10.0 45.2 52.2 0.766 86.7 81 None — 7.0 45.1 54.4 0.435 88.7 82 i₃-1 0.10 7.0 45.2 57.7 0.141 91.8 83 i₃-2 0.10 7.0 45.1 57.4 0.147 92.4 84 i₃-3 0.10 7.0 45.0 57.4 0.146 92.5 85 i₃-4 0.10 7.0 45.1 57.6 0.143 92.6 86 i₃-5 0.10 7.0 45.4 57.6 0.142 92.1

According to the methods of Test Nos. 82 to 86 (the methods of the present invention) wherein the flotation is effected in the presence of an amphoteric compound shown in Table III-9 at a specific pH, as compared with those of Test Nos. 80 and 81 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp.

Example III-11

Deinking test was carried out according to the method described in Example III-1 by using amphoteric compounds shown in Tables III-10 and IIII-23. The results are shown in Table III-23.

TABLE III-23 Residual ink Amphoteric compound Whiteness (%) area ratio (%) Test Compound Amount pH in Before After After Recovery No. No. added (%) flotation flotation flotation flotation of pulp (%) 87 None — 10.0 45.2 52.4 0.754 86.7 88 None — 7.0 45.2 54.3 0.440 88.6 89 j₃-1 0.10 7.0 45.2 57.6 0.142 92.3 90 j₃-2 0.10 7.0 45.3 57.4 0.150 92.4 91 j₃-3 0.10 7.0 45.1 57.3 0.153 92.2 92 j₃-4 0.10 7.0 45.0 57.6 0.147 91.5 93 j₃-5 0.10 7.0 45.2 57.7 0.141 91.6

According to the methods of Test Nos. 89 to 93 (the methods of the present invention) wherein the flotation is effected in the presence of an amphoteric compound shown in Table III-10 at a specific pH, as compared with those of Test Nos. 87 and 88 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp.

Example III-12

Deinking test was carried out according to the method described in Example III-1 by using amphoteric compounds shown in Tables III-11 and III-12, and Table III-24. The results are shown in Table III-24.

TABLE III-24 Residual ink Amphoteric compound Whiteness (%) area ratio (%) Test Compound Amount pH in Before After After Recovery No. No. added (%) flotation flotation flotation flotation of pulp (%) 94 None — 10.0 45.2 52.2 0.763 86.5 95 None — 7.0 45.4 54.3 0.439 88.6 96 k₃-1 0.30 7.0 45.3 57.9 0.136 91.8 97 k₃-2 0.30 7.0 45.4 57.8 0.138 91.4 98 k₃-3 0.30 7.0 45.3 57.9 0.136 91.4 99 l₃-1 0.30 7.0 45.4 58.0 0.135 91.0 100 l₃-2 0.30 7.0 45.5 57.5 0.142 92.2 101 l₃-3 0.30 7.0 45.2 57.5 0.143 92.4

According to the methods of Test Nos. 96 to 101 (the methods of the present invention) wherein the flotation is effected in the presence of an amphoteric compound shown in Table III-11 or III-12 at a specific pH, as compared with those of Test Nos. 94 and 95 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp.

Example III-13

Deinking test was carried out in a similar manner as that in Example I-7 except that the pH of the pulp slurries were each adjusted to a value shown in Table III-25 and that amphoteric compounds shown in Tables III-1, III-2 and III-3, and Table III-25 were used instead of the cationic compounds. The results thereof are shown in Table III-25.

TABLE III-25 Deinking Residual ink agent No. Amphoteric compound Whiteness (%) area ratio (%) Test (See Table Compd. Amount pH in Before After After Recovery No. I-12) No. added (%) flotation flotation flotation flotation of pulp (%) 102 A1 None — 10.0 43.9 51.0 0.841 88.5 103 A2 None — 10.0 44.0 52.2 0.785 86.5 104 A3 None — 10.0 44.6 52.1 0.771 86.2 105 A4 None — 10.0 47.8 53.5 0.415 90.0 106 A1 a₃-1 0.10 7.0 44.2 56.2 0.210 91.5 107 A2 a₃-2 0.10 7.0 44.3 57.3 0.158 90.4 108 A3 b₃-6 0.10 7.0 44.6 57.1 0.166 89.5 109 A4 c₃-1 0.05 7.0 47.0 58.1 0.161 93.4

According to the methods of Test Nos. 106 to 109 (the methods of the present invention) wherein various deinking agents are each used and the flotation is effected in the presence of an amphoteric compound at a specific pH, as compared with those of Test Nos. 102 to 105 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp.

Example III-14

Deinking test was carried out in a similar manner as that in Example I-8 except that the Ca²⁺ ion concentrations and the pH of the pulp slurries were each adjusted to a value shown in Table III-26 and that amphoteric compounds shown in Tables III-1, III-2 and III-3, and Table III-26 were used instead of the cationic compounds.

The results thereof are shown in Table III-26.

TABLE III-26 Residual ink Amphoteric compound Whiteness (%) area ratio (%) Test Compound Amount pH in Ca²⁺ ion concen- Before After After Recovery No. No. added (%) flotation tration (ppm) flotation flotation flotation of pulp (%) 110 None — 10.0 0 44.8 52.1 0.770 86.4 111 None — 10.0 50 45.0 52.2 0.752 86.8 112 None — 10.0 100 45.3 52.5 0.743 87.3 113 None — 10.0 200 45.2 52.6 0.739 87.3 114 None — 10.0 400 45.0 52.3 0.765 87.6 115 None — 10.0 800 44.7 51.8 0.781 87.6 116 a₃-1 0.06 7.0 0 44.4 57.3 0.162 93.4 117 a₃-1 0.06 7.0 50 44.9 57.7 0.157 93.0 118 a₃-1 0.06 7.0 100 44.9 58.5 0.100 92.6 119 a₃-1 0.06 7.0 200 45.2 59.2 0.095 93.0 120 a₃-1 0.06 7.0 400 44.7 57.6 0.136 93.7 121 a₃-1 0.06 7.0 800 44.6 56.8 0.230 94.1 122 b₃-1 0.10 7.0 0 44.3 56.6 0.156 93.2 123 b₃-1 0.10 7.0 200 45.3 58.6 0.099 92.8 124 b₃-1 0.10 7.0 800 44.5 56.1 0.232 93.0 125 c₃-2 0.03 7.0 0 44.4 56.8 0.158 91.7 126 c₃-2 0.03 7.0 200 45.1 58.7 0.091 91.3 127 c₃-2 0.03 7.0 800 44.7 56.3 0.241 92.4 Note) The Ca²⁺ ion concentrations in the above Table were determined in flotation.

According to the methods of Test Nos. 116 to 127 (the methods of the present invention) wherein the flotation is effected in the presence of an amphoteric compound at a specific pH at a specific Ca²⁺ ion concentration, as compared with those of Test Nos. 110 to 115 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation.

Example III-15

Deinking test was carried out in a similar manner as that in Example I-9 except that the Al³⁺ ion concentrations, the Ca²⁺ ion concentrations and the pH of the pulp slurries were each adjusted to a value shown in Table III-27 and that amphoteric compounds shown in Tables III-1, III-2 and III-3, and Table III-27 were used instead of the cationic compounds. For the adjustment of the Ca²⁺ ion concentration, CaCi₂ was used, and for the adjustment of Al³⁺ ion concentration, white water resulting from paper-making, or the white water and aluminum sulfate (in Test Nos. 131, 135 and 139) was(were) used. Further, for the adjustment of pH, hydrochloric acid or sodium hydroxide was used.

The results thereof are shown in Table III-27.

TABLE III-27 Residual ink Amphoteric compound Whiteness (%) area ratio (%) Test Compd. Amount pH in Al³⁺ ion Ca²⁺ ion Before After After Recovery No. No. added (%) flotation conc. (ppm) conc. (ppm) flotation flotation flotation of pulp (%) 128 None — 10.0 0 100 45.3 52.5 0.743 87.3 129 None — 10.0 20 100 45.5 52.2 0.776 85.2 130 None — 10.0 40 100 44.4 51.9 0.802 82.7 131 None — 10.0 60 100 43.4 51.7 0.822 79.3 132 a₃-1 0.06 7.0 0 100 44.9 58.5 0.100 92.7 133 a₃-1 0.06 7.0 20 100 45.1 57.8 0.133 90.6 134 a₃-1 0.06 7.0 40 100 44.4 56.6 0.239 88.3 135 a₃-1 0.06 7.0 60 100 43.3 54.0 0.463 85.0 136 b₃-1 0.06 7.0 20 100 45.2 57.2 0.137 90.3 137 b₃-1 0.06 7.0 60 100 43.4 53.4 0.576 84.7 138 c₃-2 0.06 7.0 20 100 45.0 57.3 0.129 88.8 139 c₃-2 0.06 7.0 60 100 43.2 53.5 0.568 83.2 Note) The Al³⁺ ion concentrations and the Ca²⁺ ion concentrations in the above Table were determined in flotation.

According to the methods of Test Nos. 132 to 139 (the methods of the present invention) wherein the flotation is effected in the presence of an amphoteric compound at a specific pH at a specific Ca²⁺ ion concentration, as compared with those of Test Nos. 128 to 131 (comparative methods), an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp there can be attained. Further, when Al³⁺ ion concentration of the slurry in flotation is 40 ppm or less, it can be expected to obtain qualities superior thereto.

Example III-16

Waste papers (news papers/leaflets=75/25) recovered in a city were treated according to the following deinking methods, and the performances of the pulp sheet thus obtained were evaluated in the same manner as that in Example I-1. The results thereof are shown in Table III-28.

In this Example, the Ca²⁺ ion concentration of the warm water had been adjusted with CaCl₂, while the Al³⁺ ion concentration thereof had been adjusted with white water resulting from paper-making.

(1) Test Nos. 140 and 141

The pulp sheet were prepared in a similar manner as that in Example I-10-(1) except that the Al³⁺ ion concentrations, the Ca²⁺ ion concentrations and the pH of the pulp slurries were each adjusted to a value shown in Table III-28.

(2) Test Nos. 142 and 143

The pulp sheet were prepared in a similar manner as that in Example I-10-(2) except that the Al³⁺ ion concentrations, the Ca²⁺ ion concentrations and the pH of the pulp slurries were each adjusted to a value shown in Table III-28. In Test No. 142, aluminum sulfate was also added to the pulp slurry to adjust the Al³⁺ concentration of the slurry to a value shown in Table III-28.

(3) Test Nos. 144 to 146

The pulp sheet were prepared in a similar manner as that in Example I-10-(3) except that the Al³⁺ ion concentrations, the Ca²⁺ ion concentrations and the pH of the pulp slurries were each adjusted to a value shown in Table III-28 and that amphoteric compounds shown in Tables III-1, III-2 and III-3, and Table III-28 were used instead of the cationic compounds.

TABLE III-28 Nonionic compound or Residual ink amphoteric compound Whiteness (%) area ratio (%) Test Name or number pH in Al³⁺ ion Ca²⁺ ion Before After After Recovery No. of compound flotation conc. (ppm) conc. (ppm) flotation flotation flotation of pulp (%) 140 None 4.5 30 5 42.2 52.9 0.683 87.8 141 None 7.0 15 200 42.1 52.8 0.690 87.1 142 NP-800 4.5 60 5 44.4 53.6 0.409 77.6 143 NP-800 7.0 15 200 44.6 53.4 0.418 78.2 144 a₃-1 7.0 15 200 45.3 58.3 0.113 90.3 145 b₃-5 7.0 15 200 45.4 58.2 0.118 90.1 146 c₃-5 7.0 15 200 45.3 57.9 0.120 89.7 Note) The Al³⁺ ion concentrations and the Ca²⁺ ion concentrations in the above Table were determined in flotation.

It is observed in Test Nos. 140 and 141 (comparative examples) that a lot of non-liberated ink spots which have not been removed from pulp by flotation is present in the reclaimed paper since the deinking agent having a poor power for liberating ink is used in the disintegrating step of waste papers. Accordingly, the reclaimed pulp is poor in quality. In Test Nos. 142 and 143 (comparative examples), the addition of the polyacrylamide optionally with aluminum sulfate causes the re-adhesion of ink to cellulose fibers, and reduces the quality of the reclaimed pulp. Further, it is observed that foaming in flotation is extremely enhanced to deteriorate the recovery of pulp.

In contrast, according to the methods of Test Nos. 144 to 146 (the methods of the present invention) wherein the flotation is effected in the presence of an amphoteric compound at a specific pH at a specific Ca²⁺ ion concentration and at a specific Al³⁺ ion concentration, an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp are observed.

Example III-17

Deinking test was carried out according to the method described in Example III-1 by using amphoteric compound m₃-1 represented by the following formula:

The results are shown in Table III-14.

TABLE III-29 Amphoteric polymer Residual ink Content of weight-average Whiteness (%) area ratio (%) Test Compd. cationic molecular Amount pH in Before After After Recovery No. No. nitrogen* (%) weight added (%) flotation flotation flotation flotation of pulp (%) 147 None — — — 10.0 45.0 52.2 0.752 86.8 148 None — — — 9.0 45.4 52.8 0.683 87.2 149 None — — — 8.0 44.9 53.3 0.411 88.3 150 None — — — 7.0 45.6 53.6 0.365 88.9 151 None — — — 6.0 45.0 54.0 0.329 88.9 152 None — — — 5.0 44.6 53.1 0.431 89.1 153 None — — — 4.0 44.3 52.9 0.625 87.6 154 m₃-1 4.65 15,000 0.01 9.0 44.8 55.7 0.264 87.1 155 m₃-1 4.65 l5,000 0.01 8.0 45.0 57.7 0.145 89.3 156 m₃-1 4.65 15,000 0.01 7.0 45.2 58.1 0.138 90.2 157 m₃-1 4.65 15,000 0.01 6.0 44.8 57.8 0.148 89.5 158 m₃-1 4.65 15,000 0.01 5.0 44.7 57.3 0.167 89.4 159 m₃-1 4.65 15,000 0.01 4.0 44.8 56.7 0.231 88.3 Note) *The content (%) of cationic nitrogen was calculated by multiplying the nitrogen content (%) determined by Kjeldahl method by the ratio of the cationic nitrogen to the total nitrogen which was determined from the molecular formula of the polymer.

In the tests described above, Test No. 147 is effected in a similar manner as that of a conventional industrial deinking method. According to the methods of Test Nos. 154 to 159 (the methods of the present invention) wherein the flotation is effected in the presence of an amphoteric compound at a specific pH, as compared with those of Test Nos. 147 to 153 (comparative methods), there can be expected to attain an improvement in whiteness of the reclaimed paper, a reduction of residual ink spots in the reclaimed paper and an increase in the recovery of pulp, by the selective removal of ink in flotation. 

What is claimed is:
 1. A deinking method comprising the following steps: (1) a first step wherein ink is liberated from waste paper as a raw material in the presence of at least one non-ionic surfactant under alkaline conditions, wherein said non-ionic surfactant is a reaction product obtained by adding an alkylene oxide to a mixture of oil and fat and an alcohol; (2) a second step wherein the ink liberated in the first step is removed in a flotation system and prevented from re-adhering to the waste paper as raw material, said second step comprising at least one step, which is carried out in the presence of at least one member selected from the group consisting of amines and acid salts of amines in an amount of from 0.01 to 1.0% by weight based on the weight of the wastepaper, wherein the pH is lower in comparison to the pH of the first step and is in the range of 4 to 9; and wherein the amines and acid salts of amines are selected from the group consisting of compounds represented by the formulas (a₂) to (h₂) and polymers represented by the formulas (i₂) to (l₂), each of which has an amino-nitrogen content of 0.01 to 35% by weight and a weight-average molecular weight of 2,000 to 3,000,000:

 in formulas (a₂) to (h₂), R₁ represents an alkyl, alkenyl or β-hydroxyalkyl group having 8 to 36 carbon atoms; R₂ and R₃ may be the same or different from each other and each represents a hydrogen atom, an alkyl group having 1 to 24 carbon atoms or an alkenyl group having 2 to 24 carbon atoms; HA represents an inorganic or organic acid; AO represents an oxyalkylene group having 2 to 4 carbon atoms; 1 and m are each zero or a positive integer with the proviso that 1 plus m is an integer of 1 to 300; and W₁, W₂, W₃ and W₄ may be the same or different from one another and each represents a hydrogen atom or an alkyl group having 1 to 24 carbon atoms;

 in formulas (i₂) to (l₂), R₁ represents an alkyl group having 1 to 24 carbon atoms or an alkenyl group having 2 to 24 carbon atoms; R₂, R₃ and R₆ may be the same or different from one another and each represents a hydrogen atom, an alkyl group having 1 to 24 carbon atoms or an alkenyl group having 2 to 24 carbon atoms; R₄ and R₅ may be the same or different from each other and each represents a hydrogen atom or a methyl group; HA represents an inorganic or organic acid; Y represents 0 or NH; p represents an integer of 1 to 10; and l, m and n are each such a positive number that the weight-average molecular weight of the polymer would be a value in the range of from 2,000 to 3,000,000.
 2. The deinking method according to claim 1, which comprises maintaining the calcium ion concentration of the flotation system at a concentration of from 10 to 400 ppm.
 3. The deinking method according to claim 2, wherein said calcium ion concentration of the flotation system is from 100 to 250 ppm.
 4. The deinking method according to claim 1, which comprises maintaining the aluminum ion concentration of the flotation system at a concentration of from 0 to 40 ppm.
 5. The deinking method of claim 1, wherein the pH in the second step is in the range of 6 to
 8. 